Joint arthroplasty devices and surgical tools

ABSTRACT

Disclosed herein are methods, compositions and tools for repairing articular surfaces repair materials and for repairing an articular surface. The articular surface repairs are customizable or highly selectable by patient and geared toward providing optimal fit and function. The surgical tools are designed to be customizable or highly selectable by patient to increase the speed, accuracy and simplicity of performing total or partial arthroplasty.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 12/606,844, entitled“Joint Arthroplasty Devices and Surgical Tools,” filed Oct. 27, 2009,which is a continuation of U.S. Ser. No. 10/724,010, entitled “PatientSelectable Joint Arthroplasty Devices and Surgical Tools FacilitatingIncreased Accuracy, Speed and Simplicity in Performing Total and PartialJoint Arthroplasty,” filed Nov. 25, 2003, which is acontinuation-in-part of U.S. Ser. No. 10/305,652 entitled “METHODS ANDCOMPOSITIONS FOR ARTICULAR REPAIR,” filed Nov. 27, 2002, which is acontinuation-in-part of U.S. Ser. No. 10/160,667, filed May 28, 2002,which in turn claims the benefit of U.S. Ser. No. 60/293,488 entitled“METHODS TO IMPROVE CARTILAGE REPAIR SYSTEMS”, filed May 25, 2001, U.S.Ser. No. 60/363,527, entitled “NOVEL DEVICES FOR CARTILAGE REPAIR, filedMar. 12, 2002 and U.S. Ser. Nos. 60/380,695 and 60/380,692, entitled“METHODS AND COMPOSITIONS FOR CARTILAGE REPAIR,” (Attorney Docket Number6750-0005p2) and “METHODS FOR JOINT REPAIR,” (Attorney Docket Number6750-0005p3), filed May 14, 2002, all of which applications are herebyincorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to orthopedic methods, systems andprosthetic devices and more particularly relates to methods, systems anddevices for articular resurfacing. The present invention also includessurgical molds designed to achieve optimal cut planes in a joint inpreparation for installation of a joint implant.

BACKGROUND OF THE INVENTION

There are various types of cartilage, e.g., hyaline cartilage andfibrocartilage. Hyaline cartilage is found at the articular surfaces ofbones, e.g., in the joints, and is responsible for providing the smoothgliding motion characteristic of moveable joints. Articular cartilage isfirmly attached to the underlying bones and measures typically less than5 mm in thickness in human joints, with considerable variation dependingon joint and site within the joint. In addition, articular cartilage isaneural, avascular, and alymphatic. In adult humans, this cartilagederives its nutrition by a double diffusion system through the synovialmembrane and through the dense matrix of the cartilage to reach thechondrocyte, the cells that are found in the connective tissue ofcartilage.

Adult cartilage has a limited ability of repair; thus, damage tocartilage produced by disease, such as rheumatoid and/or osteoarthritis,or trauma can lead to serious physical deformity and debilitation.Furthermore, as human articular cartilage ages, its tensile propertieschange. The superficial zone of the knee articular cartilage exhibits anincrease in tensile strength up to the third decade of life, after whichit decreases markedly with age as detectable damage to type II collagenoccurs at the articular surface. The deep zone cartilage also exhibits aprogressive decrease in tensile strength with increasing age, althoughcollagen content does not appear to decrease. These observationsindicate that there are changes in mechanical and, hence, structuralorganization of cartilage with aging that, if sufficiently developed,can predispose cartilage to traumatic damage.

For example, the superficial zone of the knee articular cartilageexhibits an increase in tensile strength up to the third decade of life,after which it decreases markedly with age as detectable damage to typeII collagen occurs at the articular surface. The deep zone cartilagealso exhibits a progressive decrease in tensile strength with increasingage, although collagen content does not appear to decrease. Theseobservations indicate that there are changes in mechanical and, hence,structural organization of cartilage with aging that, if sufficientlydeveloped, can predispose cartilage to traumatic damage.

Once damage occurs, joint repair can be addressed through a number ofapproaches. One approach includes the use of matrices, tissue scaffoldsor other carriers implanted with cells (e.g., chondrocytes, chondrocyteprogenitors, stromal cells, mesenchymal stem cells, etc.). Thesesolutions have been described as a potential treatment for cartilage andmeniscal repair or replacement. See, also, International Publications WO99/51719 to Fofonoff, published Oct. 14, 1999; WO01/91672 to Simon etal., published Dec. 6, 2001; and WO01/17463 to Mannsmann, published Mar.15, 2001; U.S. Pat. No. 6,283,980 B1 to Vibe-Hansen et al., issued Sep.4, 2001, U.S. Pat. No. 5,842,477 to Naughton issued Dec. 1, 1998, U.S.Pat. No. 5,769,899 to Schwartz et al. issued Jun. 23, 1998, U.S. Pat.No. 4,609,551 to Caplan et al. issued Sep. 2, 1986, U.S. Pat. No.5,041,138 to Vacanti et al. issued Aug. 29, 1991, U.S. Pat. No.5,197,985 to Caplan et al. issued Mar. 30, 1993, U.S. Pat. No. 5,226,914to Caplan et al. issued Jul. 13, 1993, U.S. Pat. No. 6,328,765 toHardwick et al. issued Dec. 11, 2001, U.S. Pat. No. 6,281,195 to Ruegeret al. issued Aug. 28, 2001, and U.S. Pat. No. 4,846,835 to Grandeissued Jul. 11, 1989. However, clinical outcomes with biologicreplacement materials such as allograft and autograft systems and tissuescaffolds have been uncertain since most of these materials cannotachieve a morphologic arrangement or structure similar to or identicalto that of normal, disease-free human tissue it is intended to replace.Moreover, the mechanical durability of these biologic replacementmaterials remains uncertain.

Usually, severe damage or loss of cartilage is treated by replacement ofthe joint with a prosthetic material, for example, silicone, e.g. forcosmetic repairs, or metal alloys. See, e.g., U.S. Pat. No. 6,383,228 toSchmotzer, issued May 7, 2002; U.S. Pat. No. 6,203,576 to Afriat et al.,issued Mar. 20, 2001; U.S. Pat. No. 6,126,690 to Ateshian, et al.,issued Oct. 3, 2000. Implantation of these prosthetic devices is usuallyassociated with loss of underlying tissue and bone without recovery ofthe full function allowed by the original cartilage and, with somedevices, serious long-term complications associated with the loss ofsignificant amount of tissue and bone can include infection, osteolysisand also loosening of the implant.

Further, joint arthroplasties are highly invasive and require surgicalresection of the entire or the majority of the articular surface of oneor more bones. With these procedures, the marrow space is reamed inorder to fit the stem of the prosthesis. The reaming results in a lossof the patient's bone stock. U.S. Pat. No. 5,593,450 to Scott et al.issued Jan. 14, 1997 discloses an oval domed shaped patella prosthesis.The prosthesis has a femoral component that includes two condyles asarticulating surfaces. The two condyles meet to form a second trochleargroove and ride on a tibial component that articulates with respect tothe femoral component. A patella component is provided to engage thetrochlear groove. U.S. Pat. No. 6,090,144 to Letot et al. issued Jul.18, 2000 discloses a knee prosthesis that includes a tibial componentand a meniscal component that is adapted to be engaged with the tibialcomponent through an asymmetrical engagement.

Another joint subject to invasive joint procedures is the hip. U.S. Pat.No. 6,262,948 to Storer et al. issued Sep. 30, 2003 discloses a femoralhip prosthesis that replaces the natural femoral head. U.S. PatentPublications 2002/0143402 A1 and 2003/0120347 to Steinberg publishedOct. 3, 2002 and Jun. 26, 2003, respectively, also disclose a hipprosthesis that replaces the femoral head and provides a member forcommunicating with the ball portion of the socket within the hip joint.

A variety of materials can be used in replacing a joint with aprosthetic, for example, silicone, e.g. for cosmetic repairs, orsuitable metal alloys are appropriate. See, e.g., U.S. Pat. No.6,443,991 B1 to Running issued Sep. 3, 2002, U.S. Pat. No. 6,387,131 B1to Miehlke et al. issued May 14, 2002; U.S. Pat. No. 6,383,228 toSchmotzer issued May 7, 2002; U.S. Pat. No. 6,344,059 B1 to Krakovits etal. issued Feb. 5, 1002; U.S. Pat. No. 6,203,576 to Afriat et al. issuedMar. 20, 2001; U.S. Pat. No. 6,126,690 to Ateshian et al. issued Oct. 3,2000; U.S. Pat. No. 6,013,103 to Kaufman et al. issued Jan. 11, 2000.Implantation of these prosthetic devices is usually associated with lossof underlying tissue and bone without recovery of the full functionallowed by the original cartilage and, with some devices, seriouslong-term complications associated with the loss of significant amountsof tissue and bone can cause loosening of the implant. One suchcomplication is osteolysis. Once the prosthesis becomes loosened fromthe joint, regardless of the cause, the prosthesis will then need to bereplaced. Since the patient's bone stock is limited, the number ofpossible replacement surgeries is also limited for joint arthroplasty.

As can be appreciated, joint arthroplasties are highly invasive andrequire surgical resection of the entire, or a majority of the,articular surface of one or more bones involved in the repair. Typicallywith these procedures, the marrow space is fairly extensively reamed inorder to fit the stem of the prosthesis within the bone. Reaming resultsin a loss of the patient's bone stock and over time subsequentosteolysis will frequently lead to loosening of the prosthesis. Further,the area where the implant and the bone mate degrades over timerequiring the prosthesis to eventually be replaced. Since the patient'sbone stock is limited, the number of possible replacement surgeries isalso limited for joint arthroplasty. In short, over the course of 15 to20 years, and in some cases even shorter time periods, the patient canrun out of therapeutic options ultimately resulting in a painful,non-functional joint.

A variety of tools are available to assist surgeons in performing jointsurgery. In the knee, for example, U.S. Pat. No. 4,501,266 to McDanielissued Feb. 26, 1985 discloses a knee distraction device thatfacilitates knee arthroplasty. The device has an adjustable forcecalibration mechanism that enables the device to accommodate controlledselection of the ligament-tensioning force to be applied to therespective, opposing sides of the knee. U.S. Pat. No. 5,002,547 toPoggie et al. issued Mar. 26, 1991 discloses a modular apparatus for usein preparing the bone surface for implantation of a modular total kneeprosthesis. The apparatus has cutting guides, templates, alignmentdevices along with a distractor and clamping instruments that providemodularity and facilitate bone resection and prosthesis implantation.U.S. Pat. No. 5,250,050 to Poggie et al. issued Oct. 5, 1993 is alsodirected to a modular apparatus for use in preparing a bone surface forthe implantation of a modular total knee prosthesis. U.S. Pat. No.5,387,216 to Thornhill et al. issued Feb. 7, 1995 disclosesinstrumentation for use in knee revision surgery. A bearing sleeve isprovided that is inserted into the damaged canal in order to take upadditional volume. The rod passes through the sleeve and is positionedto meet the natural canal of the bone. The rod is then held in a fixedposition by the bearing sleeve. A cutting guide can then be mounted onthe rod for cutting the bone and to provide a mounting surface for theimplant. U.S. Pat. No. 6,056,756 to Eng et al. issued May 2, 2000discloses a tool for preparing the distal femoral end for a prostheticimplant. The tool lays out the resection for prosthetic replacement andincludes a jack for pivotally supporting an opposing bone such that thejack raises the opposing bone in flexion to the spacing of the intendedprosthesis. U.S. Pat. No. 6,106,529 to Techiera issued Aug. 22, 2000discloses an epicondylar axis referencing drill guide for use inresection to prepare a bone end for prosthetic joint replacement. U.S.Pat. No. 6,296,646 to Williamson issued Oct. 2, 2001 discloses a systemthat allows a practitioner to position the leg in the alignment that isdirected at the end of the implant procedure and to cut both the femurand tibia while the leg is fixed in alignment. U.S. Pat. No. 6,620,168to Lombardi et al. issued Sep. 16, 2003 discloses a tool forintermedullary revision surgery along with tibial components.

U.S. Pat. No. 5,578,037 to Sanders et al. issued Nov. 26, 1996 disclosesa surgical guide for femoral resection. The guide enables a surgeon toresect a femoral neck during a hip arthroplasty procedure so that thefemoral prosthesis can be implanted to preserve or closely approximatethe anatomic center of rotation of the hip.

U.S. Pat. No. 6,206,927 to Fell, et al., issued Mar. 27, 2001, and U.S.Pat. No. 6,558,421 to Fell, et al., issued May 6, 2003, disclose asurgically implantable knee prosthesis that does not require boneresection. This prosthesis is described as substantially elliptical inshape with one or more straight edges. Accordingly, these devices arenot designed to substantially conform to the actual shape (contour) ofthe remaining cartilage in vivo and/or the underlying bone. Thus,integration of the implant can be extremely difficult due to differencesin thickness and curvature between the patient's surrounding cartilageand/or the underlying subchondral bone and the prosthesis.

Interpositional knee devices that are not attached to both the tibia andfemur have been described. For example, Platt et al. (1969) “MouldArthroplasty of the Knee,” Journal of Bone and Joint Surgery51B(1):76-87, describes a hemi-arthroplasty with a convex undersurfacethat was not rigidly attached to the tibia. Devices that are attached tothe bone have also been described. Two attachment designs are commonlyused. The McKeever design is a cross-bar member, shaped like a “t” froma top perspective view, that extends from the bone mating surface of thedevice such that the “t” portion penetrates the bone surface while thesurrounding surface from which the “t” extends abuts the bone surface.See McKeever, “Tibial Plateau Prosthesis,” Chapter 7, p. 86. Analternative attachment design is the Macintosh design, which replacesthe “t” shaped fin for a series of multiple flat serrations or teeth.See Potter, “Arthroplasty of the Knee with Tibial Metallic Implants ofthe McKeever and Macintosh Design,” Surg. Clins. Of North Am. 49(4):903-915 (1969).

U.S. Pat. No. 4,502,161 to Wall issued Mar. 5, 1985, describes aprosthetic meniscus constructed from materials such as silicone rubberor Teflon with reinforcing materials of stainless steel or nylonstrands. U.S. Pat. No. 4,085,466 to Goodfellow et al. issued Mar. 25,1978, describes a meniscal component made from plastic materials.Reconstruction of meniscal lesions has also been attempted withcarbon-fiber-polyurethane-poly (L-lactide). Leeslag, et al., Biologicaland Biomechanical Performance of Biomaterials (Christel et al., eds.)Elsevier Science Publishers B.V., Amsterdam. 1986. pp. 347-352.Reconstruction of meniscal lesions is also possible with bioresorbablematerials and tissue scaffolds.

However, currently available devices do not always provide idealalignment with the articular surfaces and the resultant joint congruity.Poor alignment and poor joint congruity can, for example, lead toinstability of the joint. In the knee joint, instability typicallymanifests as a lateral instability of the joint.

Thus, there remains a need for compositions for joint repair, includingmethods and compositions that facilitate the integration between thecartilage replacement system and the surrounding cartilage. There isalso a need for tools that increase the accuracy of cuts made to thebone in a joint in preparation for surgical implantation of, forexample, an artificial joint.

SUMMARY OF THE INVENTION

The present invention provides novel devices and methods for replacing aportion (e.g., diseased area and/or area slightly larger than thediseased area) of a joint (e.g., cartilage and/or bone) with anon-pliable, non-liquid (e.g., hard) implant material, where the implantachieves a near anatomic fit with the surrounding structures andtissues. In cases where the devices and/or methods include an elementassociated with the underlying articular bone, the invention alsoprovides that the bone-associated element achieves a near anatomicalignment with the subchondral bone. The invention also provides for thepreparation of an implantation site with a single cut, or a fewrelatively small cuts.

In one aspect, the invention includes a method for providing articularreplacement material, the method comprising the step of producingarticular replacement (e.g., cartilage replacement material) of selecteddimensions (e.g., size, thickness and/or curvature).

In another aspect, the invention includes a method of making cartilagerepair material, the method comprising the steps of (a) measuring thedimensions (e.g., thickness, curvature and/or size) of the intendedimplantation site or the dimensions of the area surrounding the intendedimplantation site; and (b) providing cartilage replacement material thatconforms to the measurements obtained in step (a). In certain aspects,step (a) comprises measuring the thickness of the cartilage surroundingthe intended implantation site and measuring the curvature of thecartilage surrounding the intended implantation site. In otherembodiments, step (a) comprises measuring the size of the intendedimplantation site and measuring the curvature of the cartilagesurrounding the intended implantation site. In other embodiments, step(a) comprises measuring the thickness of the cartilage surrounding theintended implantation site, measuring the size of the intendedimplantation site, and measuring the curvature of the cartilagesurrounding the intended implantation site. In other embodiments, step(a) comprises reconstructing the shape of healthy cartilage surface atthe intended implantation site.

In any of the methods described herein, one or more components of thearticular replacement material (e.g., the cartilage replacementmaterial) can be non-pliable, non-liquid, solid or hard. The dimensionsof the replacement material can be selected following intraoperativemeasurements. Measurements can also be made using imaging techniquessuch as ultrasound, MRI, CT scan, x-ray imaging obtained with x-ray dyeand fluoroscopic imaging. A mechanical probe (with or without imagingcapabilities) can also be used to select dimensions, for example anultrasound probe, a laser, an optical probe and a deformable material ordevice.

In any of the methods described herein, the replacement material can beselected (for example, from a pre-existing library of repair systems),grown from cells and/or hardened from various materials. Thus, thematerial can be produced pre- or post-operatively. Furthermore, in anyof the methods described herein the repair material can also be shaped(e.g., manually, automatically or by machine), for example usingmechanical abrasion, laser ablation, radiofrequency ablation,cryoablation and/or enzymatic digestion.

In any of the methods described herein, the articular replacementmaterial can comprise synthetic materials (e.g., metals, liquid metals,polymers, alloys or combinations thereof) or biological materials suchas stem cells, fetal cells or chondrocyte cells.

In another aspect, the invention includes a method of repairing acartilage in a subject, the method of comprising the step of implantingcartilage repair material prepared according to any of the methodsdescribed herein.

In yet another aspect, the invention provides a method of determiningthe curvature of an articular surface, the method comprising the step ofintraoperatively measuring the curvature of the articular surface usinga mechanical probe. The articular surface can comprise cartilage and/orsubchondral bone. The mechanical probe (with or without imagingcapabilities) can include, for example an ultrasound probe, a laser, anoptical probe and/or a deformable material.

In a still further aspect, the invention provides a method of producingan articular replacement material comprising the step of providing anarticular replacement material that conforms to the measurementsobtained by any of the methods of described herein.

In a still further aspect, the invention includes a partial or fullarticular prosthesis comprising a first component comprising a cartilagereplacement material; and an optional second component comprising one ormore metals, wherein said second component can have a curvature similarto subchondral bone, wherein said prosthesis comprises less than about80% of the articular surface. In certain embodiments, the first and/orsecond component comprises a non-pliable material (e.g., a metal, apolymer, a metal alloy, a solid biological material). Other materialsthat can be included in the first and/or second components includepolymers, biological materials, metals, metal alloys or combinationsthereof. Furthermore, one or both components can be smooth or porous (orporous coated) using any methods or mechanisms to achieve in-growth ofbone known in the art. In certain embodiments, the first componentexhibits biomechanical properties (e.g., elasticity, resistance to axialloading or shear forces) similar to articular cartilage. The firstand/or second component can be bioresorbable and, in addition, the firstor second components can be adapted to receive injections.

In another aspect, an articular prosthesis comprising an externalsurface located in the load bearing area of an articular surface,wherein the dimensions of said external surface achieve a near anatomicfit with the adjacent, underlying or opposing cartilage is provided. Theprosthesis can comprise one or more metals or metal alloys.

In yet another aspect, an articular repair system comprising (a)cartilage replacement material, wherein said cartilage replacementmaterial has a curvature similar to surrounding, adjacent, underlying oropposing cartilage; and (b) at least one non-biologic material, whereinsaid articular surface repair system comprises a portion of thearticular surface equal to, smaller than, or greater than, theweight-bearing surface that is provided. In certain embodiments, thecartilage replacement material is non-pliable (e.g., hardhydroxyapatite, etc.). In certain embodiments, the system exhibitsbiomechanical (e.g., elasticity, resistance to axial loading or shearforces) and/or biochemical properties similar to articular cartilage.The first and/or second component can be bioresorbable and, in addition,the first or second components can be adapted to receive injections.

In a still further aspect of the invention, an articular surface repairsystem comprising a first component comprising a cartilage replacementmaterial, wherein said first component has dimensions similar to that ofadjacent, surrounding, underlying or opposing cartilage; and a secondcomponent, wherein said second component has a curvature similar tosubchondral bone, wherein said articular surface repair system comprisesless than about 80% of the articular surface (e.g., a single femoralcondyle, tibia, etc.) is provided. In certain embodiments, the firstcomponent is non-pliable (e.g., hard hydroxyapatite, etc.). In certainembodiments, the system exhibits biomechanical (e.g., elasticity,resistance to axial loading or shear forces) and/or biochemicalproperties similar to articular cartilage. The first and/or secondcomponent can be bioresorbable and, in addition, the first or secondcomponents can be adapted to receive injections. In certain embodiments,the first component has a curvature and thickness similar to that ofadjacent, underlying, opposing or surrounding cartilage. The thicknessand/or curvature can vary across the implant material.

In a still further embodiment, a partial articular prosthesis comprising(a) a metal or metal alloy; and (b) an external surface located in theload bearing area of an articular surface, wherein the external surfacedesigned to achieve a near anatomic fit with the adjacent surrounding,underlying or opposing cartilage is provided.

Any of the repair systems or prostheses described herein (e.g., theexternal surface) can comprise a polymeric material, for exampleattached to said metal or metal alloy. Any of the repair systems can beentirely composed of polymer. Further, any of the systems or prosthesesdescribed herein can be adapted to receive injections, for example,through an opening in the external surface of said cartilage replacementmaterial (e.g., an opening in the external surface terminates in aplurality of openings on the bone surface). Bone cement, polymers,Liquid Metal, therapeutics, and/or other bioactive substances can beinjected through the opening(s). In certain embodiments, bone cement isinjected under pressure in order to achieve permeation of portions ofthe marrow space with bone cement. In addition, any of the repairsystems or prostheses described herein can be anchored in bone marrow orin the subchondral bone itself. One or more anchoring extensions (e.g.,pegs, pins, etc.) can extend through the bone and/or bone marrow.

In any of the embodiments and aspects described herein, the joint can bea knee, shoulder, hip, vertebrae, elbow, ankle, wrist etc.

In another aspect, a method of designing an articular implant comprisingthe steps of obtaining an image of a joint, wherein the image includesboth normal cartilage and diseased cartilage; reconstructing dimensionsof the diseased cartilage surface to correspond to normal cartilage; anddesigning the articular implant to match the dimensions of thereconstructed diseased cartilage surface or to match an area slightlygreater than the diseased cartilage surface is provided. The image canbe, for example, an intraoperative image including a surface detectionmethod using any techniques known in the art, e.g., mechanical, opticalultrasound, and known devices such as MRI, CT, ultrasound, digitaltomosynthesis and/or optical coherence tomography images. In certainembodiments, reconstruction is performed by obtaining a surface thatfollows the contour of the normal cartilage. The surface can beparametric and include control points that extend the contour of thenormal cartilage to the diseased cartilage and/or a B-spline surface. Inother embodiments, the reconstruction is performed by obtaining a binaryimage of cartilage by extracting cartilage from the image, whereindiseased cartilage appears as indentations in the binary image; andperforming, for example, a morphological closing operation (e.g.,performed in two or three dimensions using a structuring element and/ora dilation operation followed by an erosion operation) to determine theshape of an implant to fill the areas of diseased cartilage.

In yet another aspect, described herein are systems for evaluating thefit of an articular repair system into a joint, the systems comprisingone or more computing means capable of superimposing a three-dimensional(e.g., three-dimensional representations of at least one articularstructure and of the articular repair system) or a two-dimensionalcross-sectional image (e.g., cross-sectional images reconstructed inmultiple planes) of a joint and an image of an articular repair systemto determine the fit of the articular repair system. The computing meanscan be: capable of merging the images of the joint and the articularrepair system into a common coordinate system; capable of selecting anarticular repair system having the best fit; capable of rotating ormoving the images with respect to each other; and/or capable ofhighlighting areas of poor alignment between the articular repair systemand the surrounding articular surfaces. The three-dimensionalrepresentations can be generated using a parametric surfacerepresentation.

In yet another aspect, surgical tools for preparing a joint to receivean implant are described, for example a tool comprising one or moresurfaces or members that conform at least partially to the shape of thearticular surfaces of the joint (e.g., a femoral condyle and/or tibialplateau of a knee joint). In certain embodiments, the tool comprisesLucite silastic and/or other polymers or suitable materials. The toolcan be re-useable or single-use. The tool can be comprised of a singlecomponent or multiple components. In certain embodiments, the toolcomprises an array of adjustable, closely spaced pins. In anyembodiments described herein, the surgical tool can be designed tofurther comprise an aperture therein, for example one or more apertureshaving dimensions (e.g., diameter, depth, etc.) smaller or equal to oneor more dimensions of the implant and/or one or more apertures adaptedto receive one or more injectables. Any of the tools described hereincan further include one or more curable (hardening) materials orcompositions, for example that are injected through one or moreapertures in the tool and which solidify to form an impression of thearticular surface.

In still another aspect, a method of evaluating the fit of an articularrepair system into a joint is described herein, the method comprisingobtaining one or more three-dimensional images (e.g., three-dimensionalrepresentations of at least one articular structure and of the articularrepair system) or two-dimensional cross-sectional images (e.g.,cross-sectional images reconstructed in multiple planes) of a joint,wherein the joint includes at least one defect or diseased area;obtaining one or more images of one or more articular repair systemsdesigned to repair the defect or diseased area; and evaluating theimages to determine the articular repair system that best fits thedefect (e.g., by superimposing the images to determine the fit of thearticular repair system into the joint). In certain embodiments, theimages of the joint and the articular repair system are merged into acommon coordinate system. The three-dimensional representations can begenerated using a parametric surface representation. In any of thesemethods, the evaluation can be performed by manual visual inspectionand/or by computer (e.g., automated). The images can be obtained, forexample, using a C-arm system and/or radiographic contrast.

In yet another aspect, described herein is a method of placing animplant into an articular surface having a defect or diseased area, themethod comprising the step of imaging the joint using a C-arm systemduring placement of the implant, thereby accurately placing the implantinto a defect or diseased area.

Also disclosed is a customizable, or patient specific, implantconfigured for placement between joint surfaces formed by inserting ahollow device having an aperture and a lumen into a target joint, andinjecting material into the hollow device to form an implant.

A customizable, or patient specific, implant configured for placementbetween joint surfaces is also disclosed wherein the implant is formedby inserting a retaining device that engages at least a portion of onejoint surface in a joint and injecting material into an aperture of theretaining device to form an implant.

The invention is also directed to tools. A is disclosed that toolcomprises: a mold having a surface for engaging a joint surface; a blockthat communicates with the mold; and at least one guide aperture in theblock.

Another tool is disclosed that is formed at least partially in situ andcomprises: a mold formed in situ using at least one of an inflatablehollow device or a retaining device to conform to the joint surface onat least one surface having a surface for engaging a joint surface; ablock that communicates with the mold; and at least one guide aperturein the block.

A method of placing an implant into a joint is also provided. The methodcomprises the steps of imaging the joint using a C-arm system, obtaininga cross-sectional image with the C-arm system, and utilizing the imagefor placing the implant into a joint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart depicting various methods of the present inventionincluding, measuring the size of an area of diseased cartilage orcartilage loss, measuring the thickness of the adjacent cartilage, andmeasuring the curvature of the articular surface and/or subchondralbone. Based on this information, a best-fitting implant can be selectedfrom a library of implants or a patient specific custom implant can begenerated. The implantation site is subsequently prepared and theimplantation is performed.

FIG. 2 is a reproduction of a three-dimensional thickness map of thearticular cartilage of the distal femur. Three-dimensional thicknessmaps can be generated, for example, from ultrasound, CT or MRI data.Dark holes within the substances of the cartilage indicate areas of fullthickness cartilage loss.

FIG. 3 A shows an example of a Placido disc of concentrically arrangedcircles of light. FIG. 3 B shows an example of a projected Placido discon a surface of fixed curvature.

FIG. 4 shows a reflection resulting from a projection of concentriccircles of light (Placido Disk) on each femoral condyle, demonstratingthe effect of variation in surface contour on the reflected circles.

FIG. 5 shows an example of a 2D topographical map of an irregularlycurved surface.

FIG. 6 shows an example of a 3D topographical map of an irregularlycurved surface.

FIGS. 7 A-H illustrate, in cross-section, various stages of kneeresurfacing. FIG. 7 A shows an example of normal thickness cartilage anda cartilage defect. FIG. 7 B shows an imaging technique or a mechanical,optical, laser or ultrasound device measuring the thickness anddetecting a sudden change in thickness indicating the margins of acartilage defect. FIG. 7 C shows a weight-bearing surface mapped ontothe articular cartilage. FIG. 7 D shows an intended implantation siteand cartilage defect. FIG. 7 E depicts placement of an exemplary singlecomponent articular surface repair system. FIG. 7 F shows an exemplarymulti-component articular surface repair system. FIG. 7 G shows anexemplary single component articular surface repair system. FIG. 7 Hshows an exemplary multi-component articular surface repair system.

FIGS. 8 A-E, illustrate, in cross-section, exemplary knee imaging andresurfacing. FIG. 8 A shows a magnified view of an area of diseasedcartilage. FIG. 8 B shows a measurement of cartilage thickness adjacentto the defect. FIG. 8 C depicts placement of a multi-componentmini-prosthesis for articular resurfacing. FIG. 8 D is a schematicdepicting placement of a single component mini-prosthesis utilizingstems or pegs. FIG. 8 E depicts placement of a single componentmini-prosthesis utilizing stems and an opening for injection of bonecement.

FIGS. 9 A-C, illustrate, in cross-section, other exemplary kneeresurfacing devices and methods. FIG. 9 A depicts normal thicknesscartilage in the anterior and central and posterior portion of a femoralcondyle and a large area of diseased cartilage in the posterior portionof the femoral condyle. FIG. 9 B depicts placement of a single componentarticular surface repair system. FIG. 9 c depicts a multi-componentarticular surface repair system.

FIGS. 10 A-B are flow charts illustrating steps for forming a device insitu.

FIGS. 11 A-G illustrate, in cross-section, the use of an inflationdevice to form an implant. FIG. 11 A illustrates a single lumen ballooninserted between two joint surfaces where the inflation occurs withinthe bounds of the joint. FIG. 11 B illustrates another single lumenballoon inserted between two joint surfaces where the inflatablesurfaces extend beyond a first and second edge of a joint. FIG. 11 Cillustrates another single lumen balloon between two joint surfaces.FIG. 11 D illustrates a multi-balloon solution using two balloons wherethe balloons are adjacent to each other within the joint. FIG. 11 Eillustrates an alternative multi-balloon solution wherein a firstballoon is comprised within a second balloon. FIG. 11 F illustratesanother multi-balloon solution where a first balloon lies within thelumen of a second balloon and further wherein the second balloon isadjacent a third balloon. FIG. 11 G illustrates a 3 balloonconfiguration wherein a first balloon lies adjacent a second balloon anda third balloon fits within the lumen of one of the first or secondballoon.

FIGS. 12 A-E illustrate a variety of cross-sectional shapes achievedusing balloons with variable wall thicknesses or material compositions.In FIG. 12 A the inflation device enables the implant to achieve asurface conforming to the irregularities of the joint surface. In FIG.12 B the inflation device enables the implant to achieve a surface thatsits above the irregular joint surface; FIG. 12 c illustrates a deviceformed where a central portion of the device sits above the jointsurface irregularities while the proximal and distal ends illustratedform a lateral abutting surface to the joint defects. FIG. 12 Dillustrates a device formed using a first inflation device within asecond inflation device, with an exterior configuration similar to thatshown in FIG. 12 A; while FIG. 12 E illustrates an alternative deviceformed using at least two different inflation devices having an exteriorshape similar to the device shown in FIG. 12 c.

FIGS. 13 A-J(1-3) show a variety of cross-sectional views of theinflation devices shown in FIGS. 11 and 12 taken at a positionperpendicular to the views shown in FIGS. 11 and 12.

FIGS. 14 A-J illustrate the use of a retaining device to form an implantin situ.

FIGS. 15 A-B show single and multiple component devices. FIG. 15 A showsan exemplary single component articular surface repair system withvarying curvature and radii. FIG. 15 B depicts a multi-componentarticular surface repair system with a second component that mirrors theshape of the subchondral bone and a first component closely matches theshape and curvature of the surrounding normal cartilage.

FIGS. 16 A-B show exemplary articular repair systems having an outercontour matching the surrounding normal cartilage. The systems areimplanted into the underlying bone using one or more pegs.

FIG. 17 shows a perspective view of an exemplary articular repair deviceincluding a flat surface to control depth and prevent toggle; anexterior surface having the contour of normal cartilage; flanges toprevent rotation and control toggle; a groove to facilitate tissuein-growth.

FIGS. 18 A-D depict, in cross-section, another example of an implantwith multiple anchoring pegs. FIG. 18 B-D show various cross-sectionalrepresentations of the pegs: FIG. 18 B shows a peg having a groove;

FIG. 18 C shows a peg with radially-extending arms that help anchor thedevice in the underlying bone; and FIG. 18 D shows a peg with multiplegrooves or flanges.

FIG. 19 A-B depict an overhead view of an exemplary implant withmultiple anchoring pegs and depict how the pegs are not necessarilylinearly aligned along the longitudinal axis of the device.

FIGS. 20 A-E depict an exemplary implant having radially extending arms.FIGS. 20 B-E are overhead views of the implant showing that the shape ofthe peg need not be conical.

FIG. 21 A illustrates a femur, tibia and fibula along with themechanical and anatomic axes. FIGS. 21 B-E illustrate the tibia with theanatomic and mechanical axis used to create a cutting plane along with acut femur and tibia. FIG. 21 F illustrates the proximal end of the femurincluding the head of the femur.

FIG. 22 shows an example of a surgical tool having one surface matchingthe geometry of an articular surface of the joint. Also shown is anaperture in the tool capable of controlling drill depth and width of thehole and allowing implantation of an insertion of implant having apress-fit design.

FIG. 23 is a flow chart depicting various methods of the invention usedto create a mold for preparing a patient's joint for arthroscopicsurgery.

FIG. 24 A depicts, in cross-section, an example of a surgical toolcontaining an aperture through which a surgical drill or saw can fit.The aperture guides the drill or saw to make the proper hole or cut inthe underlying bone. Dotted lines represent where the cut correspondingto the aperture will be made in bone. FIG. 24 B depicts, incross-section, an example of a surgical tool containing aperturesthrough which a surgical drill or saw can fit and which guide the drillor saw to make cuts or holes in the bone. Dotted lines represent wherethe cuts corresponding to the apertures will be made in bone.

FIGS. 25 A-Q illustrate tibial cutting blocks and molds used to create asurface perpendicular to the anatomic axis for receiving the tibialportion of a knee implant.

FIGS. 26 A-O illustrate femur cutting blocks and molds used to create asurface for receiving the femoral portion of a knee implant.

FIG. 27 A-G illustrate patellar cutting blocks and molds used to preparethe patella for receiving a portion of a knee implant.

FIG. 28 A-H illustrate femoral head cutting blocks and molds used tocreate a surface for receiving the femoral portion of a knee implant.

FIG. 29 A-D illustrate acetabulum cutting blocks and molds used tocreate a surface for a hip implant.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable any person skilled inthe art to make and use the invention. Various modifications to theembodiments described will be readily apparent to those skilled in theart, and the generic principles defined herein can be applied to otherembodiments and applications without departing from the spirit and scopeof the present invention as defined by the appended claims. Thus, thepresent invention is not intended to be limited to the embodimentsshown, but is to be accorded the widest scope consistent with theprinciples and features disclosed herein. To the extent necessary toachieve a complete understanding of the invention disclosed, thespecification and drawings of all issued patents, patent publications,and patent applications cited in this application are incorporatedherein by reference.

As will be appreciated by those of skill in the art, the practice of thepresent invention employs, unless otherwise indicated, conventionalmethods of x-ray imaging and processing, x-ray tomosynthesis, ultrasoundincluding A-scan, B-scan and C-scan, computed tomography (CT scan),magnetic resonance imaging (MRI), optical coherence tomography, singlephoton emission tomography (SPECT) and positron emission tomography(PET) within the skill of the art. Such techniques are explained fullyin the literature and need not be described herein. See, e.g., X-RayStructure Determination: A Practical Guide, 2nd Edition, editors Stoutand Jensen, 1989, John Wiley & Sons, publisher; Body CT: A PracticalApproach, editor Slone, 1999, McGraw-Hill publisher; X-ray Diagnosis: APhysician's Approach, editor Lam, 1998 Springer-Verlag, publisher; andDental Radiology: Understanding the X-Ray Image, editor LaetitiaBrocklebank 1997, Oxford University Press publisher. See also, TheEssential Physics of Medical Imaging (2^(nd) Ed.), Jerrold T. Bushberg,et al.

The present invention provides methods and compositions for repairingjoints, particularly for repairing articular cartilage and forfacilitating the integration of a wide variety of cartilage repairmaterials into a subject. Among other things, the techniques describedherein allow for the customization of cartilage repair material to suita particular subject, for example in terms of size, cartilage thicknessand/or curvature. When the shape (e.g., size, thickness and/orcurvature) of the articular cartilage surface is an exact or nearanatomic fit with the non-damaged cartilage or with the subject'soriginal cartilage, the success of repair is enhanced. The repairmaterial can be shaped prior to implantation and such shaping can bebased, for example, on electronic images that provide informationregarding curvature or thickness of any “normal” cartilage surroundingthe defect and/or on curvature of the bone underlying the defect. Thus,the current invention provides, among other things, for minimallyinvasive methods for partial joint replacement. The methods will requireonly minimal or, in some instances, no loss in bone stock. Additionally,unlike with current techniques, the methods described herein will helpto restore the integrity of the articular surface by achieving an exactor near anatomic match between the implant and the surrounding oradjacent cartilage and/or subchondral bone.

Advantages of the present invention can include, but are not limited to,(i) customization of joint repair, thereby enhancing the efficacy andcomfort level for the patient following the repair procedure; (ii)eliminating the need for a surgeon to measure the defect to be repairedintraoperatively in some embodiments; (iii) eliminating the need for asurgeon to shape the material during the implantation procedure; (iv)providing methods of evaluating curvature of the repair material basedon bone or tissue images or based on intraoperative probing techniques;(v) providing methods of repairing joints with only minimal or, in someinstances, no loss in bone stock; and (vi) improving postoperative jointcongruity.

Thus, the methods described herein allow for the design and use of jointrepair material that more precisely fits the defect (e.g., site ofimplantation) and, accordingly, provides improved repair of the joint.

I. Assessment of Joints and Alignment

The methods and compositions described herein can be used to treatdefects resulting from disease of the cartilage (e.g., osteoarthritis),bone damage, cartilage damage, trauma, and/or degeneration due tooveruse or age. The invention allows, among other things, a healthpractitioner to evaluate and treat such defects. The size, volume andshape of the area of interest can include only the region of cartilagethat has the defect, but preferably will also include contiguous partsof the cartilage surrounding the cartilage defect.

As will be appreciated by those of skill in the art, size, curvatureand/or thickness measurements can be obtained using any suitabletechnique. For example, one-dimensional, two-dimensional, and/orthree-dimensional measurements can be obtained using suitable mechanicalmeans, laser devices, electromagnetic or optical tracking systems,molds, materials applied to the articular surface that harden and“memorize the surface contour,” and/or one or more imaging techniquesknown in the art. Measurements can be obtained non-invasively and/orintraoperatively (e.g., using a probe or other surgical device). As willbe appreciated by those of skill in the art, the thickness of the repairdevice can vary at any given point depending upon the depth of thedamage to the cartilage and/or bone to be corrected at any particularlocation on an articular surface.

As illustrated in FIG. 1, typically the process begins by firstmeasuring the size of the area of diseased cartilage or cartilage loss10. Thereafter the user can optionally measure the thickness of adjacentcartilage 20. Once these steps are performed, the curvature of thearticular surface is measured 30. Alternatively, the curvature ofsubchondral bone can be measured.

Once the size of the defect is known, either an implant can be selectedfrom a library 32 or an implant can be generated based on the patientspecific parameters obtained in the measurements and evaluation 34.Prior to installing the implant in the joint, the implantation site isprepared 40 and then the implant is installed 42. One or more of thesesteps can be repeated as necessary or desired as shown by the optionalrepeat steps 11, 21, 31, 33, 35, and 41.

A. Imaging Techniques

I. Thickness and Curvature

As will be appreciated by those of skill in the art, imaging techniquessuitable for measuring thickness and/or curvature (e.g., of cartilageand/or bone) or size of areas of diseased cartilage or cartilage lossinclude the use of x-rays, magnetic resonance imaging (MRI), computedtomography scanning (CT, also known as computerized axial tomography orCAT), optical coherence tomography, ultrasound imaging techniques, andoptical imaging techniques. (See, also, International Patent PublicationWO 02/22014 to Alexander, et al., published Mar. 21, 2002; U.S. Pat. No.6,373,250 to Tsoref et al., issued Apr. 16, 2002; and Vandeberg et al.(2002) Radiology 222:430-436). Contrast or other enhancing agents can beemployed using any route of administration, e.g. intravenous,intra-articular, etc.

In certain embodiments, CT or MRI is used to assess tissue, bone,cartilage and any defects therein, for example cartilage lesions orareas of diseased cartilage, to obtain information on subchondral boneor cartilage degeneration and to provide morphologic or biochemical orbiomechanical information about the area of damage. Specifically,changes such as fissuring, partial or full thickness cartilage loss, andsignal changes within residual cartilage can be detected using one ormore of these methods. For discussions of the basic NMR principles andtechniques, see MRI Basic Principles and Applications, Second Edition,Mark A. Brown and Richard C. Semelka, Wiley-Liss, Inc. (1999). For adiscussion of MRI including conventional T1 and T2-weighted spin-echoimaging, gradient recalled echo (GRE) imaging, magnetization transfercontrast (MTC) imaging, fast spin-echo (FSE) imaging, contrast enhancedimaging, rapid acquisition relaxation enhancement (RARE) imaging,gradient echo acquisition in the steady state (GRASS), and drivenequilibrium Fourier transform (DEFT) imaging, to obtain information oncartilage, see Alexander, et al., WO 02/22014. Other techniques includesteady state free precision, flexible equilibrium MRI and DESS. Thus, inpreferred embodiments, the measurements produced are based onthree-dimensional images of the joint obtained as described inAlexander, et al., WO 02/22014 or sets of two-dimensional imagesultimately yielding 3D information. Two-dimensional, andthree-dimensional images, or maps, of the cartilage alone or incombination with a movement pattern of the joint, e.g.flexion—extension, translation and/or rotation, can be obtained.Three-dimensional images can include information on movement patterns,contact points, contact zone of two or more opposing articular surfaces,and movement of the contact point or zone during joint motion. Two- andthree-dimensional images can include information on biochemicalcomposition of the articular cartilage. In addition, imaging techniquescan be compared over time, for example to provide up-to-date informationon the shape and type of repair material needed.

As will be appreciated by those of skill in the art, imaging techniquescan be combined, if desired. For example, C-arm imaging or x-rayfluoroscopy can be used for motion imaging, while MRI can yield highresolution cartilage information. C-arm imaging can be combined withintra-articular contrast to visualize the cartilage.

Any of the imaging devices described herein can also be usedintra-operatively (see, also below), for example using a hand-heldultrasound and/or optical probe to image the articular surfaceintra-operatively. FIG. 2 illustrates a reproduction of athree-dimensional thickness map of the articular surface on the distalfemur. The dark holes within the cartilage indicate areas of fullcartilage loss.

ii. Anatomical and Mechanical Axes

Imaging can be used to determine the anatomical and biomechanical axesof an extremity associated with a joint. Suitable tests include, forexample, an x-ray, or an x-ray combined with an MRI. Typically,anatomical landmarks are identified on the imaging test results (e.g.,the x-ray film) and those landmarks are then utilized to directly orindirectly determine the desired axes. Thus, for example, if surgery iscontemplated in a hip joint, knee joint, or ankle joint, an x-ray can beobtained. This x-ray can be a weight-bearing film of the extremity, forexample, a full-length leg film taken while the patient is standing.This film can be used to determine the femoral and tibial anatomicalaxes and to estimate the biomechanical axes. As will be appreciated bythose of skill in the art, these processes for identifying, e.g.,anatomical and biomechanical axis of the joint can be applied to otherjoints without departing from the scope of the invention.

Anatomical and biomechanical axes can also be determined using otherimaging modalities, including but not limited to, computed tomographyand MRI. For example, a CT scan can be obtained through the hip joint,the knee joint, and the ankle joint. Optionally, the scan can bereformatted in the sagittal, coronal, or other planes. The CT images canthen be utilized to identify anatomical landmarks and to determine theanatomical and biomechanical axes of the hip joint, knee joint, and/orankle joint. Similarly, an MRI scan can be obtained for this purpose.For example, an MRI scan of the thigh and pelvic region can be obtainedusing a body coil or a torso phased array coil. A high resolution scanof the knee joint can be obtained using a dedicated extremity coil. Ascan of the calf/tibia region and the ankle joint can be obtained againusing a body coil or a torso phased array coil. Anatomical landmarks canbe identified in each joint on these scans and the anatomical andbiomechanical axes can be estimated using this information.

An imaging test obtained during weight-bearing conditions has someinherent advantages, in that it demonstrates normal as well aspathological loading and load distribution. A cross-sectional imagingstudy such as a CT scan or MRI scan has some advantages because itallows one to visualize and demonstrate the anatomical landmarks inthree, rather than two, dimensions, thereby adding accuracy. Moreover,measurements can be performed in other planes, such as the sagittal oroblique planes, that may not be easily accessible in certain anatomicalregions using conventional radiography. In principle, any imaging testcan be utilized for this purpose.

The biomechanical axis can be defined as the axis going from the centerof the femoral head, between the condylar surfaces and through the anklejoint.

Computed Tomography imaging has been shown to be highly accurate for thedetermination of the relative anatomical and biomechanical axes of theleg (Testi Debora, Zannoni Cinzia, Cappello Angelo and Viceconti Marco.“Border tracing algorithm implementation for the femoral geometryreconstruction.” Comp. Meth. and Programs in Biomed., Feb. 14, 2000;Farrar M J, Newman R J, Mawhinney R R, King R. “Computed tomography scanscout film for measurement of femoral axis in knee arthroplasty.” J.Arthroplasty. 1999 December; 14(8): 1030-1; Kim J S, Park T S, Park S B,Kim J S, Kim I Y, Kim S I. “Measurement of femoral neck anteversion in3D. Part 1: 3D imaging method.” Med. and Biol. Eng. and Computing.38(6): 603-609, November 2000; Akagi M, Yamashita E, Nakagawa T, AsanoT, Nakamura T. “Relationship between frontal knee alignment andreference axis in the distal femur.” Clin. Ortho. and Related Res. No.388, 147-156, 2001; Mahaisavariya B, Sitthiseripratip K, Tongdee T,Bohez E, Sloten J V, Oris P. “Morphological study of the proximal femur:a new method of geometrical assessment using 3 dimensional reverseengineering.” Med. Eng. and Phys. 24 (2002) 617-622; Lam Li On,Shakespeare D. “Varus/Valgus alignment of the femoral component in totalknee arthroplasty.” The Knee, 10 (2003) 237-241).

The angles of the anatomical structures of the proximal and distal femuralso show a certain variability level (i.e. standard deviation)comparable with the varus or valgus angle or the angle between theanatomical femoral axis and the biomechanical axis (Mahaisavariya B,Sitthiseripratip K, Tongdee T, Bohez E, Sloten J V, Oris P.“Morphological study of the proximal femur: a new method of geometricalassessment using 3 dimensional reverse engineering.” Med. Eng. and Phys.24 (2002) 617-622). Thus, a preferred approach for assessing the axes isbased on CT scans of the hip, knee and ankle joint or femur rather thanonly of the knee region.

CT has been shown to be efficient in terms of the contrast of the bonetissue with respect to surrounding anatomical tissue so the bonestructures corresponding to the femur and tibia can be extracted veryaccurately with semi automated computerized systems (Mahaisavariya B,Sitthiseripratip K, Tongdee T, Bohez E, Sloten J V, Oris P.“Morphological study of the proximal femur: a new method of geometricalassessment using 3 dimensional reverse engineering.” Med. Eng. and Phys.24 (2002) 617-622; Testi Debora, Zannoni Cinzia, Cappello Angelo andViceconti Marco. “Border tracing algorithm implementation for thefemoral geometry reconstruction.” Comp. Meth. and Programs in Biomed.,Feb. 14, 2000).

While 2-D CT has been shown to be accurate in the estimation of thebiomechanical axis (Mahaisavariya B, Sitthiseripratip K, Tongdee T,Bohez E, Sloten J V, Oris P. “Morphological study of the proximal femur:a new method of geometrical assessment using 3 dimensional reverseengineering.” Med. Eng. and Phys. 24 (2002) 617-622; Testi Debora,supra.; Lam Li On, Supra, 3-D CT has been shown to be more accurate forthe estimation of the femoral anteversion angle (Kim J S, Park T S, ParkS B, Kim J S, Kim I Y, Kim S I. Measurement of femoral neck anteversionin 3D. Part 1: 3D imaging method. Medical and Biological engineering andcomputing. 38(6): 603-609, November 2000; Kim J S, Park T S, Park S B,Kim J S, Kim I Y, Kim S I. Measurement of femoral neck anteversion in3D. Part 1: 3D modeling method. Medical and Biological engineering andcomputing. 38(6): 610-616, November 2000). Farrar used simple CT 2-Dscout views to estimate the femoral axis (Farrar M J, Newman R J,Mawhinney R R, King R. Computed tomography scan scout film formeasurement of femoral axis in knee arthroplasty. J. Arthroplasty. 1999December; 14(8): 1030-1).

In one embodiment, 2-D sagittal and coronal reconstructions of CT sliceimages are used to manually estimate the biomechanical axis. One skilledin the art can easily recognize many different ways to automate thisprocess. For example, a CT scan covering at least the hip, knee andankle region is acquired. This results in image slices (axial) which canbe interpolated to generate the sagittal and coronal views.

Preprocessing (filtering) of the slice images can be used to improve thecontrast of the bone regions so that they can be extracted accuratelyusing simple thresholding or a more involved image segmentation toollike LiveWire or active contour models.

Identification of landmarks of interest like the centroid of the tibialshaft, the ankle joint, the intercondylar notch and the centroid of thefemoral head can be performed. The biomechanical axis can be defined asthe line connecting the proximal and the distal centroids, i.e. thefemoral head centroid, the tibial or ankle joint centroid. The positionof the intercondylar notch can be used for evaluation of possibledeviations, errors or deformations including varus and valgus deformity.

In one embodiment, multiple imaging tests can be combined. For example,the anatomical and biomechanical axes can be estimated using aweight-bearing x-ray of the extremity or portions of the extremity. Theanatomical information derived in this fashion can then be combined witha CT or MRI scan of one or more joints, such as a hip, knee, or anklejoint. Landmarks seen on radiography can then, for example, becross-referenced on the CT or MRI scan. Axis measurements performed onradiography can be subsequently applied to the CT or MRI scans or otherimaging modalities. Similarly, the information obtained from a CT scancan be compared with that obtained with an MRI or ultrasound scan. Inone embodiment, image fusion of different imaging modalities can beperformed. For example, if surgery is contemplated in a knee joint, afull-length weight-bearing x-ray of the lower extremity can be obtained.This can be supplemented by a spiral CT scan, optionally withintra-articular contrast of the knee joint providing high resolutionthree-dimensional anatomical characterization of the knee anatomy evenincluding the menisci and cartilage. This information, along with theaxis information provided by the radiograph can be utilized to select orderive therapies, such as implants or surgical instruments.

In certain embodiments, it may be desirable to characterize the shapeand dimension of intra-articular structures, including subchondral boneor the cartilage. This can be done using a CT scan, preferably a spiralCT scan of one or more joints. The spiral CT scan can optionally beperformed using intra-articular contrast. Alternatively, an MRI scan canbe performed. If CT is utilized, a full spiral scan, or a few selectedslices, can be obtained through neighboring joints. Typically, a fullspiral scan providing full three-dimensional characterization would beobtained in the joint for which therapy is contemplated. If implants, ormolds, for surgical instruments are selected or shaped, using this scan,the subchondral bone shape can be accurately determined from theresultant image data. A standard cartilage thickness and, similarly, astandard cartilage loss can be assumed in certain regions of thearticular surface. For example, a standard thickness of 2 mm of thearticular cartilage can be applied to the subchondral bone in theanterior third of the medial and lateral femoral condyles. Similarly, astandard thickness of 2 mm of the articular cartilage can be applied tothe subchondral bone in the posterior third of the medial and lateralfemoral condyles. A standard thickness of 0 mm of the articularcartilage can be applied in the central weight-bearing zone of themedial condyle, and a different value can be applied to the lateralcondyle. The transition between these zones can be gradual, for example,from 2 mm to 0 mm. These standard values of estimated cartilagethickness and cartilage loss in different regions of the joint canoptionally be derived from a reference database. The reference databasecan include categories such as age, body mass index (“BMI”), severity ofdisease, pain, severity of varus deformity, severity of valgusdeformity, Kellgren-Lawrence score, along with other parameters that aredetermined to be relative and useful. Use of a standard thickness forthe articular cartilage can facilitate the imaging protocols requiredfor pre-operative planning.

Alternatively, however, the articular cartilage can be fullycharacterized by performing a spiral CT scan of the joint in thepresence of intra-articular contrast or by performing an MRI scan usingcartilage sensitive pulse sequences.

The techniques described herein can be used to obtain an image of ajoint that is stationary, either weight bearing or not, or in motion orcombinations thereof. Imaging studies that are obtained during jointmotion can be useful for assessing the load bearing surface. This can beadvantageous for designing or selecting implants, e.g. for selectingreinforcements in high load areas, for surgical tools and for implantplacement, e.g. for optimizing implant alignment relative to high loadareas.

B. Intraoperative Measurements

Alternatively, or in addition to, non-invasive imaging techniquesdescribed above, measurements of the size of an area of diseasedcartilage or an area of cartilage loss, measurements of cartilagethickness and/or curvature of cartilage or bone can be obtainedintraoperatively during arthroscopy or open arthrotomy. Intraoperativemeasurements can, but need not, involve actual contact with one or moreareas of the articular surfaces.

Devices suitable for obtaining intraoperative measurements of cartilageor bone or other articular structures, and to generate a topographicalmap of the surface include but are not limited to, Placido disks andlaser interferometers, and/or deformable materials or devices. (See, forexample, U.S. Pat. Nos. 6,382,028 to Wooh et al., issued May 7, 2002;6,057,927 to Levesque et al., issued May 2, 2000; 5,523,843 to Yamane etal. issued Jun. 4, 1996; 5,847,804 to Sarver et al. issued Dec. 8, 1998;and 5,684,562 to Fujieda, issued Nov. 4, 1997).

FIG. 3 A illustrates a Placido disk of concentrically arranged circlesof light. The concentric arrays of the Placido disk project well-definedcircles of light of varying radii, generated either with laser or whitelight transported via optical fiber. The Placido disk can be attached tothe end of an endoscopic device (or to any probe, for example ahand-held probe) so that the circles of light are projected onto thecartilage surface. FIG. 3 B illustrates an example of a Placido diskprojected onto the surface of a fixed curvature. One or more imagingcameras can be used (e.g., attached to the device) to capture thereflection of the circles. Mathematical analysis is used to determinethe surface curvature. The curvature can then, for example, bevisualized on a monitor as a color-coded, topographical map of thecartilage surface. Additionally, a mathematical model of thetopographical map can be used to determine the ideal surface topographyto replace any cartilage defects in the area analyzed.

FIG. 4 shows a reflection resulting from the projection of concentriccircles of light (Placido disk) on each femoral condyle, demonstratingthe effect of variation in surface contour on reflected circles.

Similarly a laser interferometer can also be attached to the end of anendoscopic device. In addition, a small sensor can be attached to thedevice in order to determine the cartilage surface or bone curvatureusing phase shift interferometry, producing a fringe pattern analysisphase map (wave front) visualization of the cartilage surface. Thecurvature can then be visualized on a monitor as a color coded,topographical map of the cartilage surface. Additionally, a mathematicalmodel of the topographical map can be used to determine the idealsurface topography to replace any cartilage or bone defects in the areaanalyzed. This computed, ideal surface, or surfaces, can then bevisualized on the monitor, and can be used to select the curvature, orcurvatures, of the replacement cartilage.

One skilled in the art will readily recognize that other techniques foroptical measurements of the cartilage surface curvature can be employedwithout departing from the scope of the invention. For example, a2-dimentional or 3-dimensional map, such as that shown in FIG. 5 andFIG. 6, can be generated.

Mechanical devices (e.g., probes) can also be used for intraoperativemeasurements, for example, deformable materials such as gels, molds, anyhardening materials (e.g., materials that remain deformable until theyare heated, cooled, or otherwise manipulated). See, e.g., WO 02/34310 toDickson et al., published May 2, 2002. For example, a deformable gel canbe applied to a femoral condyle. The side of the gel pointing towardsthe condyle can yield a negative impression of the surface contour ofthe condyle. The negative impression can then be used to determine thesize of a defect, the depth of a defect and the curvature of thearticular surface in and adjacent to a defect. This information can beused to select a therapy, e.g. an articular surface repair system. Inanother example, a hardening material can be applied to an articularsurface, e.g. a femoral condyle or a tibial plateau. The hardeningmaterial can remain on the articular surface until hardening hasoccurred. The hardening material can then be removed from the articularsurface. The side of the hardening material pointing towards thearticular surface can yield a negative impression of the articularsurface. The negative impression can then be used to determine the sizeof a defect, the depth of a defect and the curvature of the articularsurface in and adjacent to a defect. This information can then be usedto select a therapy, e.g. an articular surface repair system. In someembodiments, the hardening system can remain in place and form theactual articular surface repair system.

In certain embodiments, the deformable material comprises a plurality ofindividually moveable mechanical elements. When pressed against thesurface of interest, each element can be pushed in the opposingdirection and the extent to which it is pushed (deformed) can correspondto the curvature of the surface of interest. The device can include abrake mechanism so that the elements are maintained in the position thatconforms to the surface of the cartilage and/or bone. The device canthen be removed from the patient and analyzed for curvature.Alternatively, each individual moveable element can include markersindicating the amount and/or degree it is deformed at a given spot. Acamera can be used to intra-operatively image the device and the imagecan be saved and analyzed for curvature information. Suitable markersinclude, but are not limited to, actual linear measurements (metric orempirical), different colors corresponding to different amounts ofdeformation and/or different shades or hues of the same color(s).Displacement of the moveable elements can also be measured usingelectronic means.

Other devices to measure cartilage and subchondral bone intraoperativelyinclude, for example, ultrasound probes. An ultrasound probe, preferablyhandheld, can be applied to the cartilage and the curvature of thecartilage and/or the subchondral bone can be measured. Moreover, thesize of a cartilage defect can be assessed and the thickness of thearticular cartilage can be determined. Such ultrasound measurements canbe obtained in A-mode, B-mode, or C-mode. If A-mode measurements areobtained, an operator can typically repeat the measurements with severaldifferent probe orientations, e.g. mediolateral and anteroposterior, inorder to derive a three-dimensional assessment of size, curvature andthickness.

One skilled in the art will easily recognize that different probedesigns are possible using the optical, laser interferometry, mechanicaland ultrasound probes. The probes are preferably handheld. In certainembodiments, the probes or at least a portion of the probe, typicallythe portion that is in contact with the tissue, can be sterile.Sterility can be achieved with use of sterile covers, for examplesimilar to those disclosed in WO 99/08598A1 to Lang, published Feb. 25,1999.

Analysis on the curvature of the articular cartilage or subchondral boneusing imaging tests and/or intraoperative measurements can be used todetermine the size of an area of diseased cartilage or cartilage loss.For example, the curvature can change abruptly in areas of cartilageloss. Such abrupt or sudden changes in curvature can be used to detectthe boundaries of diseased cartilage or cartilage defects.

As described above, measurements can be made while the joint isstationary, either weight bearing or not, or in motion.

II. Repair Materials

A wide variety of materials find use in the practice of the presentinvention, including, but not limited to, plastics, metals, crystal freemetals, ceramics, biological materials (e.g., collagen or otherextracellular matrix materials), hydroxyapatite, cells (e.g., stemcells, chondrocyte cells or the like), or combinations thereof. Based onthe information (e.g., measurements) obtained regarding the defect andthe articular surface and/or the subchondral bone, a repair material canbe formed or selected. Further, using one or more of these techniquesdescribed herein, a cartilage replacement or regenerating materialhaving a curvature that will fit into a particular cartilage defect,will follow the contour and shape of the articular surface, and willmatch the thickness of the surrounding cartilage. The repair materialcan include any combination of materials, and typically include at leastone non-pliable material, for example materials that are not easily bentor changed.

A. Metal and Polymeric Repair Materials

Currently, joint repair systems often employ metal and/or polymericmaterials including, for example, prostheses which are anchored into theunderlying bone (e.g., a femur in the case of a knee prosthesis). See,e.g., U.S. Pat. No. 6,203,576 to Afriat, et al. issued Mar. 20, 2001 and6,322,588 to Ogle, et al. issued Nov. 27, 2001, and references citedtherein. A wide-variety of metals are useful in the practice of thepresent invention, and can be selected based on any criteria. Forexample, material selection can be based on resiliency to impart adesired degree of rigidity. Non-limiting examples of suitable metalsinclude silver, gold, platinum, palladium, iridium, copper, tin, lead,antimony, bismuth, zinc, titanium, cobalt, stainless steel, nickel, ironalloys, cobalt alloys, such as Elgiloy®, a cobalt-chromium-nickel alloy,and MP35N, a nickel-cobalt-chromium-molybdenum alloy, and Nitinol™, anickel-titanium alloy, aluminum, manganese, iron, tantalum, crystal freemetals, such as Liquidmetal® alloys (available from LiquidMetalTechnologies, www.liquidmetal.com), other metals that can slowly formpolyvalent metal ions, for example to inhibit calcification of implantedsubstrates in contact with a patient's bodily fluids or tissues, andcombinations thereof.

Suitable synthetic polymers include, without limitation, polyamides(e.g., nylon), polyesters, polystyrenes, polyacrylates, vinyl polymers(e.g., polyethylene, polytetrafluoroethylene, polypropylene andpolyvinyl chloride), polycarbonates, polyurethanes, poly dimethylsiloxanes, cellulose acetates, polymethyl methacrylates, polyether etherketones, ethylene vinyl acetates, polysulfones, nitrocelluloses, similarcopolymers and mixtures thereof. Bioresorbable synthetic polymers canalso be used such as dextran, hydroxyethyl starch, derivatives ofgelatin, polyvinylpyrrolidone, polyvinyl alcohol,poly[N-(2-hydroxypropyl) methacrylamide], poly(hydroxy acids),poly(epsilon-caprolactone), polylactic acid, polyglycolic acid,poly(dimethyl glycolic acid), poly(hydroxy butyrate), and similarcopolymers can also be used.

Other materials would also be appropriate, for example, the polyketoneknown as polyetheretherketone (PEEK™). This includes the material PEEK450G, which is an unfilled PEEK approved for medical implantationavailable from Victrex of Lancashire, Great Britain. (Victrex is locatedat www.matweb.com or see Boedeker www.boedeker.com). Other sources ofthis material include Gharda located in Panoli, India(www.ghardapolymers.com).

It should be noted that the material selected can also be filled. Forexample, other grades of PEEK are also available and contemplated, suchas 30% glass-filled or 30% carbon filled, provided such materials arecleared for use in implantable devices by the FDA, or other regulatorybody. Glass filled PEEK reduces the expansion rate and increases theflexural modulus of PEEK relative to that portion which is unfilled. Theresulting product is known to be ideal for improved strength, stiffness,or stability. Carbon filled PEEK is known to enhance the compressivestrength and stiffness of PEEK and lower its expansion rate. Carbonfilled PEEK offers wear resistance and load carrying capability.

As will be appreciated, other suitable similarly biocompatiblethermoplastic or thermoplastic polycondensate materials that resistfatigue, have good memory, are flexible, and/or deflectable have verylow moisture absorption, and good wear and/or abrasion resistance, canbe used without departing from the scope of the invention. The implantcan also be comprised of polyetherketoneketone (PEKK).

Other materials that can be used include polyetherketone (PEK),polyetherketoneetherketoneketone (PEKEKK), andpolyetheretherketoneketone (PEEKK), and generally apolyaryletheretherketone. Further other polyketones can be used as wellas other thermoplastics.

Reference to appropriate polymers that can be used for the implant canbe made to the following documents, all of which are incorporated hereinby reference. These documents include: PCT Publication WO 02/02158 A1,dated Jan. 10, 2002 and entitled Bio-Compatible Polymeric Materials; PCTPublication WO 02/00275 A1, dated Jan. 3, 2002 and entitledBio-Compatible Polymeric Materials; and PCT Publication WO 02/00270 A1,dated Jan. 3, 2002 and entitled Bio-Compatible Polymeric Materials.

The polymers can be prepared by any of a variety of approaches includingconventional polymer processing methods. Preferred approaches include,for example, injection molding, which is suitable for the production ofpolymer components with significant structural features, and rapidprototyping approaches, such as reaction injection molding andstereo-lithography. The substrate can be textured or made porous byeither physical abrasion or chemical alteration to facilitateincorporation of the metal coating. Other processes are alsoappropriate, such as extrusion, injection, compression molding and/ormachining techniques. Typically, the polymer is chosen for its physicaland mechanical properties and is suitable for carrying and spreading thephysical load between the joint surfaces.

More than one metal and/or polymer can be used in combination with eachother. For example, one or more metal-containing substrates can becoated with polymers in one or more regions or, alternatively, one ormore polymer-containing substrate can be coated in one or more regionswith one or more metals.

The system or prosthesis can be porous or porous coated. The poroussurface components can be made of various materials including metals,ceramics, and polymers. These surface components can, in turn, besecured by various means to a multitude of structural cores formed ofvarious metals. Suitable porous coatings include, but are not limitedto, metal, ceramic, polymeric (e.g., biologically neutral elastomerssuch as silicone rubber, polyethylene terephthalate and/or combinationsthereof) or combinations thereof. See, e.g., U.S. Pat. No. 3,605,123 toHahn, issued Sep. 20, 1971. U.S. Pat. No. 3,808,606 to Tronzo issued May7, 1974 and U.S. Pat. No. 3,843,975 to Tronzo issued Oct. 29, 1974; U.S.Pat. No. 3,314,420 to Smith issued Apr. 18, 1967; U.S. Pat. No.3,987,499 to Scharbach issued Oct. 26, 1976; and GermanOffenlegungsschrift 2,306,552. There can be more than one coating layerand the layers can have the same or different porosities. See, e.g.,U.S. Pat. No. 3,938,198 to Kahn, et al., issued Feb. 17, 1976.

The coating can be applied by surrounding a core with powdered polymerand heating until cured to form a coating with an internal network ofinterconnected pores. The tortuosity of the pores (e.g., a measure oflength to diameter of the paths through the pores) can be important inevaluating the probable success of such a coating in use on a prostheticdevice. See, also, U.S. Pat. No. 4,213,816 to Morris issued Jul. 22,1980. The porous coating can be applied in the form of a powder and thearticle as a whole subjected to an elevated temperature that bonds thepowder to the substrate. Selection of suitable polymers and/or powdercoatings can be determined in view of the teachings and references citedherein, for example based on the melt index of each.

B. Biological Repair Material

Repair materials can also include one or more biological material eitheralone or in combination with non-biological materials. For example, anybase material can be designed or shaped and suitable cartilagereplacement or regenerating material(s) such as fetal cartilage cellscan be applied to be the base. The cells can be then be grown inconjunction with the base until the thickness (and/or curvature) of thecartilage surrounding the cartilage defect has been reached. Conditionsfor growing cells (e.g., chondrocytes) on various substrates in culture,ex vivo and in vivo are described, for example, in U.S. Pat. Nos.5,478,739 to Slivka et al. issued Dec. 26, 1995; 5,842,477 to Naughtonet al. issued Dec. 1, 1998; 6,283,980 to Vibe-Hansen et al., issued Sep.4, 2001, and 6,365,405 to Salzmann et al. issued Apr. 2, 2002.Non-limiting examples of suitable substrates include plastic, tissuescaffold, a bone replacement material (e.g., a hydroxyapatite, abioresorbable material), or any other material suitable for growing acartilage replacement or regenerating material on it.

Biological polymers can be naturally occurring or produced in vitro byfermentation and the like. Suitable biological polymers include, withoutlimitation, collagen, elastin, silk, keratin, gelatin, polyamino acids,cat gut sutures, polysaccharides (e.g., cellulose and starch) andmixtures thereof. Biological polymers can be bioresorbable.

Biological materials used in the methods described herein can beautografts (from the same subject); allografts (from another individualof the same species) and/or xenografts (from another species). See,also, International Patent Publications WO 02/22014 to Alexander et al.published Mar. 21, 2002 and WO 97/27885 to Lee published Aug. 7, 1997.In certain embodiments autologous materials are preferred, as they cancarry a reduced risk of immunological complications to the host,including re-absorption of the materials, inflammation and/or scarringof the tissues surrounding the implant site.

In one embodiment of the invention, a probe is used to harvest tissuefrom a donor site and to prepare a recipient site. The donor site can belocated in a xenograft, an allograft or an autograft. The probe is usedto achieve a good anatomic match between the donor tissue sample and therecipient site. The probe is specifically designed to achieve a seamlessor near seamless match between the donor tissue sample and the recipientsite. The probe can, for example, be cylindrical. The distal end of theprobe is typically sharp in order to facilitate tissue penetration.Additionally, the distal end of the probe is typically hollow in orderto accept the tissue. The probe can have an edge at a defined distancefrom its distal end, e.g. at 1 cm distance from the distal end and theedge can be used to achieve a defined depth of tissue penetration forharvesting. The edge can be external or can be inside the hollow portionof the probe. For example, an orthopedic surgeon can take the probe andadvance it with physical pressure into the cartilage, the subchondralbone and the underlying marrow in the case of a joint such as a kneejoint. The surgeon can advance the probe until the external or internaledge reaches the cartilage surface. At that point, the edge will preventfurther tissue penetration thereby achieving a constant and reproducibletissue penetration. The distal end of the probe can include one or moreblades, saw-like structures, or tissue cutting mechanism. For example,the distal end of the probe can include an iris-like mechanismconsisting of several small blades. The blade or blades can be movedusing a manual, motorized or electrical mechanism thereby cuttingthrough the tissue and separating the tissue sample from the underlyingtissue. Typically, this will be repeated in the donor and the recipient.In the case of an iris-shaped blade mechanism, the individual blades canbe moved so as to close the iris thereby separating the tissue samplefrom the donor site.

In another embodiment of the invention, a laser device or aradiofrequency device can be integrated inside the distal end of theprobe. The laser device or the radiofrequency device can be used to cutthrough the tissue and to separate the tissue sample from the underlyingtissue.

In one embodiment of the invention, the same probe can be used in thedonor and in the recipient. In another embodiment, similarly shapedprobes of slightly different physical dimensions can be used. Forexample, the probe used in the recipient can be slightly smaller thanthat used in the donor thereby achieving a tight fit between the tissuesample or tissue transplant and the recipient site. The probe used inthe recipient can also be slightly shorter than that used in the donorthereby correcting for any tissue lost during the separation or cuttingof the tissue sample from the underlying tissue in the donor material.

Any biological repair material can be sterilized to inactivatebiological contaminants such as bacteria, viruses, yeasts, molds,mycoplasmas and parasites. Sterilization can be performed using anysuitable technique, for example radiation, such as gamma radiation.

Any of the biological materials described herein can be harvested withuse of a robotic device. The robotic device can use information from anelectronic image for tissue harvesting.

In certain embodiments, the cartilage replacement material has aparticular biochemical composition. For instance, the biochemicalcomposition of the cartilage surrounding a defect can be assessed bytaking tissue samples and chemical analysis or by imaging techniques.For example, WO 02/22014 to Alexander describes the use of gadoliniumfor imaging of articular cartilage to monitor glycosaminoglycan contentwithin the cartilage. The cartilage replacement or regenerating materialcan then be made or cultured in a manner, to achieve a biochemicalcomposition similar to that of the cartilage surrounding theimplantation site. The culture conditions used to achieve the desiredbiochemical compositions can include, for example, varyingconcentrations. Biochemical composition of the cartilage replacement orregenerating material can, for example, be influenced by controllingconcentrations and exposure times of certain nutrients and growthfactors.

III. Devices Design

A. Cartilage Models

Using information on thickness and curvature of the cartilage, aphysical model of the surfaces of the articular cartilage and of theunderlying bone can be created. This physical model can berepresentative of a limited area within the joint or it can encompassthe entire joint. For example, in the knee joint, the physical model canencompass only the medial or lateral femoral condyle, both femoralcondyles and the notch region, the medial tibial plateau, the lateraltibial plateau, the entire tibial plateau, the medial patella, thelateral patella, the entire patella or the entire joint. The location ofa diseased area of cartilage can be determined, for example using a 3Dcoordinate system or a 3D Euclidian distance as described in WO02/22014.

In this way, the size of the defect to be repaired can be determined. Aswill be apparent, some, but not all, defects will include less than theentire cartilage. Thus, in one embodiment of the invention, thethickness of the normal or only mildly diseased cartilage surroundingone or more cartilage defects is measured. This thickness measurementcan be obtained at a single point or, preferably, at multiple points,for example 2 point, 4-6 points, 7-10 points, more than 10 points orover the length of the entire remaining cartilage. Furthermore, once thesize of the defect is determined, an appropriate therapy (e.g.,articular repair system) can be selected such that as much as possibleof the healthy, surrounding tissue is preserved.

In other embodiments, the curvature of the articular surface can bemeasured to design and/or shape the repair material. Further, both thethickness of the remaining cartilage and the curvature of the articularsurface can be measured to design and/or shape the repair material.Alternatively, the curvature of the subchondral bone can be measured andthe resultant measurement(s) can be used to either select or shape acartilage replacement material. For example, the contour of thesubchondral bone can be used to re-create a virtual cartilage surface:the margins of an area of diseased cartilage can be identified. Thesubchondral bone shape in the diseased areas can be measured. A virtualcontour can then be created by copying the subchondral bone surface intothe cartilage surface, whereby the copy of the subchondral bone surfaceconnects the margins of the area of diseased cartilage.

Turning now to FIGS. 7 A-H, various stages of knee resurfacing steps areshown. FIG. 7 A illustrates an example of normal thickness cartilage 700in the anterior, central and posterior portion of a femoral condyle 702with a cartilage defect 705 in the posterior portion of the femoralcondyle. FIG. 7 B shows the detection of a sudden change in thicknessindicating the margins of a cartilage defect 710 that would be observedusing the imaging techniques or the mechanical, optical, laser orultrasound techniques described above. FIG. 7 C shows the margins of aweight-bearing surface 715 mapped onto the articular cartilage 700.Cartilage defect 705 is located within the weight-bearing surface 715.

FIG. 7 D shows an intended implantation site (stippled line) 720 andcartilage defect 705. In this depiction, the implantation site 720 isslightly larger than the area of diseased cartilage 705. FIG. 7 Edepicts placement of a single component articular surface repair system725. The external surface of the articular surface repair system 726 hasa curvature that seamlessly extends from the surrounding cartilage 700resulting in good postoperative alignment between the surrounding normalcartilage 700 and the articular surface repair system 725.

FIG. 7 F shows an exemplary multi-component articular surface repairsystem 730. The distal surface 733 of the second component 732 has acurvature that extends from that of the adjacent subchondral bone 735.The first component 736 has a thickness t and surface curvature 738 thatextends from the surrounding normal cartilage 700. In this embodiment,the second component 732 could be formed from a material with a Shore orRockwell hardness that is greater than the material forming the firstcomponent 736, if desired. Thus it is contemplated that the secondcomponent 732 having at least portion of the component in communicationwith the bone of the joint is harder than the first component 736 whichextends from the typically naturally softer cartilage material. Otherconfigurations, of course, are possible without departing from the scopeof the invention.

By providing a softer first component 736 and a firmer second component732, the overall implant can be configured so that its relative hardnessis analogous to that of the bone-cartilage or bone-meniscus area that itabuts. Thus, the softer material first component 736, being formed of asofter material, could perform the cushioning function of the nearbymeniscus or cartilage.

FIG. 7 G shows another single component articular surface repair system740 with a peripheral margin 745 which is configured so that it issubstantially non-perpendicular to the surrounding or adjacent normalcartilage 700. FIG. 7 H shows a multi-component articular surface repairsystem 750 with a first component 751 and a second component 752 similarto that shown in FIG. 7 G with a peripheral margin 745 of the secondcomponent 745 substantially non-perpendicular to the surrounding oradjacent normal cartilage 700.

Now turning to FIGS. 8 A-E, these figures depict exemplary knee imagingand resurfacing processes. FIG. 8 A depicts a magnified view of an areaof diseased cartilage 805 demonstrating decreased cartilage thicknesswhen compared to the surrounding normal cartilage 800. The margins 810of the defect have been determined. FIG. 8 B depicts the measurement ofcartilage thickness 815 adjacent to the defect 805. FIG. 8 C depicts theplacement of a multi-component mini-prosthesis 824 for articularresurfacing. The thickness 820 of the first component 823 closelyapproximates that of the adjacent normal cartilage 800. The thicknesscan vary in different regions of the prosthesis. The curvature of thedistal portion 824 of the first component 823 closely approximates anextension of the normal cartilage 800 surrounding the defect. Thecurvature of the distal portion 826 of the second component 825 is aprojection of the surface 827 of the adjacent subchondral bone 830 andcan have a curvature that is the same, or substantially similar, to allor part of the surrounding subchondral bone.

FIG. 8 D is a schematic depicting placement of a single componentmini-prosthesis 840 utilizing anchoring stems 845. As will beappreciated by those of skill in the art, a variety o configurations,including stems, posts, and nubs can be employed. Additionally, thecomponent is depicted such that its internal surface 829 is locatedwithin the subchondral bone 830. In an alternative construction, theinterior surface 829 conforms to the surface of the subchondral bone831.

FIG. 8 E depicts placement of a single component mini-prosthesis 840utilizing anchoring stems 845 and an opening at the external surface 850for injection of bone cement 855 or other suitable material. Theinjection material 855 can freely extravasate into the adjacent bone andmarrow space from several openings at the undersurface of themini-prosthesis 860 thereby anchoring the mini-prosthesis.

FIGS. 9 A-C, depict an alternative knee resurfacing device. FIG. 9 Adepicts a normal thickness cartilage in the anterior, central andposterior portion of a femoral condyle 900 and a large area of diseasedcartilage 905 toward the posterior portion of the femoral condyle. FIG.9 B depicts placement of a single component articular surface repairsystem 910. Again, the implantation site has been prepared with a singlecut 921, as illustrated. However, as will be appreciated by those ofskill in the art, the repair system can be perpendicular to the adjacentnormal cartilage 900 without departing from the scope of the invention.The articular surface repair system is not perpendicular to the adjacentnormal cartilage 900. FIG. 9 c depicts a multi-component articularsurface repair system 920. Again, the implantation site has beenprepared with a single cut (cut line shown as 921). The second component930 has a curvature similar to the extended surface 930 adjacentsubchondral bone 935. The first component 940 has a curvature thatextends from the adjacent cartilage 900.

B. Device Modeling In Situ

Another approach to repairing a defect is to model defect repair systemin situ, as shown in FIGS. 10 A-B. As shown in FIG. 10 A, one approachwould be to insert a hollow device, such as a balloon, into the targetjoint 1000. Any device capable of accepting, for example, injections ofmaterial would be suitable. Suitable injection materials include, forexample, polymers and other materials discussed in Section II, above,can be used without departing from the scope of the invention.

In one embodiment it is contemplated that an insertion device has asubstantially fixed shape that matches at least one articular surface orsubchondral bone of the joint. After inserting the insertion device1000, material is injected into the joint through the insertion device1010 where it then hardens in situ, forming an implant 1052. Theinjection material can optionally bond to the device while hardening.

Alternatively, the implant can be removed after hardening 1020 forfurther processing 1030, such as polishing, e.g. as described SectionIV.

Where the implant is removable after hardening in situ, it can bepreferable to have the implant be formed so that it is collapsible,foldable or generally changeable in shape to facilitate removal. Afterprocessing, the implant can be reinstalled 1040.

One or more molds can be applied to one or more articular surfaces. Themold can have an internal surface facing the articular surface thatsubstantially conforms to the shape of the articular cartilage and/orthe shape of the subchondral bone. A hardening material including apolymer or metals can then be injected through an opening in the mold.The opening can include a membrane that allows insertion of an injectiondevice such as a needle. The membrane helps to avoid reflux of theinjected material into the joint cavity. Alternatively, the mold can bemade of a material that provides sufficient structural rigidity to allowhardening of the injected substance with the proper shape while allowingfor placement of needles and other devices through the mold.

Additionally, the implant device can be composed of a plurality ofsubcomponents, where the volume or size of each of the subcomponents issmaller than the volume of the implant. The different subcomponents canbe connected or assembled prior to insertion into the joint 1050(whether outside the body or adjacent the joint but within orsubstantially within the body), or, in some instances, can be assembledafter insertion to the joint 1052. The subcomponents can be disassembledinside the joint, or adjacent the joint, once hardening of theinjectable material has occurred.

Additionally, the implant can be fixed to the surface of the bone afterimplantation 1060 For example, fixation mechanisms can includemechanical structures such as fins, keels, teeth and pegs ornon-mechanical means, such as bone cement, etc. Typically after thedevice is implanted and/or fixed within the joint, the functionality ofthe implant is tested 1070 to determine whether it enables the joint toengage in a desired range of motion. As will be appreciated by those ofskill in the art, one or more of these steps can be repeated withoutdeparting from the scope of the invention, as shown by the optionalrepeat steps 1001, 1011, 1021, 1031, 1041, 1051, 1053, 1061 and 1071.

As shown in FIG. 10 B, another approach would be to insert a retainingdevice into the target joint 1002. Any device capable of accepting, forexample, injections of material would be suitable. Suitable materialsinclude, for example, polymers and other materials discussed in SectionII, above, can be used without departing from the scope of theinvention.

In one embodiment it is contemplated that an insertion device has asubstantially fixed shape that matches at least one articular surface orsubchondral bone of the joint. After inserting the retaining device1002, material is injected into a hollow area formed between theretaining device and the joint surface through an aperture 1012 where itthen hardens in situ, forming an implant 1052. The injection materialcan optionally bond to the device while hardening.

Alternatively, the implant can be removed after hardening 1020 forfurther processing 1030, such as polishing, e.g. as described SectionIV.

Where the implant is removable after hardening in situ, it can bepreferable to have the implant be formed so that it is collapsible,foldable or generally changeable in shape to facilitate removal. Afterprocessing, the implant can be reinstalled 1040.

Additionally, the implant device can be composed of a plurality ofsubcomponents, where the volume or size of each of the subcomponents issmaller than the volume of the implant. The different subcomponents canbe connected or assembled prior to insertion into the joint 1050(whether outside the body or adjacent the joint but within orsubstantially within the body), or, in some instances, can be assembledafter insertion to the joint 1052. The subcomponents can be disassembledinside the joint, or adjacent the joint, once hardening of theinjectable material has occurred.

Additionally, the implant can be fixed to the surface of the bone afterimplantation 1060 For example, fixation mechanisms can includemechanical structures such as fins, keels, teeth and pegs ornon-mechanical means, such as bone cement, etc. Typically after thedevice is implanted and/or fixed within the joint, the functionality ofthe implant is tested 1070 to determine whether it enables the joint toengage in a desired range of motion. As will be appreciated by those ofskill in the art, one or more of these steps can be repeated withoutdeparting from the scope of the invention, as shown by the optionalrepeat steps 1003, 1013, 1021, 1031, 1041, 1051, 1053, 1061 and 1071.

Prior to performing the method shown in FIG. 10 B, one or more holes orapertures can be drilled into the surface of the bone at an angle eitherperpendicular to the bone surface or set at an angle. Upon injectingmaterial underneath the retaining device, the material embeds within theholes and form pegs upon hardening.

In one contemplated embodiment, at least a portion of the implantationdevice remains in situ after hardening of the injection material. Inthis scenario, the implantation device can be formed from abio-resorbable material. In this instance, the container forming theimplantation device can be resorbed, typically some time after hardeningof the injection material.

The shape of the implantation device can be fixed. Where the shape isfixed, an imaging test or intraoperative measurement can be used toeither shape or select the best fitting device for a particular patient,for example, using the imaging techniques and intraoperative measurementtechniques described in SECTIONS IA-B, above.

In other embodiments, portions of the device can be rigid, orsubstantially rigid, while other portions of the device are deformableor malleable. Alternatively, a portion of the device can be relativelymore rigid than another portion, without any requirement that anysection be rigid, deformable or malleable, but that sections vary inhardness relative to another section. In this manner the shape of therigid, substantially rigid, or relatively more rigid section can bedetermined, for example, using an imaging test. In contrast, it ispossible that the malleable, deformable, or relatively more deformableportion of the implantation device can then take the shape of one ormore articular surface in situ. This occurs particularly after theimplantation material has been injected and while the material ishardening in situ. In still other embodiments, the entire device can bedeformable.

In other embodiments, the implantation device can be expandable orcollapsible. For example, a support structure such as a Nitinol™ meshcan be inserted into the joint. Insertion can occur via, for example, acatheter or an arthroscopy portal. Once inside the joint, theimplantation device can then be expanded. The implantation device caninclude a receptacle, such as a bag, to receive the injection ofhardening material, such as polyethylene or other liquid including metalpreparations. The receptacle portion of the implantation device can bebio-resorbable and/or can bond with the injected material.Alternatively, the implantation device can be removed subsequent toinjecting the material. Where a supporting material is used, thesupporting material can be removed concurrently or subsequent to theremoval of the implantation device, either via an incision or bycollapsing the implantation device and removing it via, for example, thecatheter or arthroscopy portal.

In another embodiment, a balloon such as that shown in FIGS. 11 A-E, canbe used as the implantation device. Different balloon shapes and sizescan be made available. A detailed description of all possible shapes andsizes for the balloons is not included to avoid obscuring the invention,but would be apparent to those of skill in the art. Where a balloon isused, it can be inserted into a joint and inflated. The size, height,shape and position of the balloon can be evaluated arthroscopically orvia an open incision or using, for example, an imaging test relative tothe articular surface and the other articular strictures. Range ofmotion testing can be performed in order to ensure adequate size, shapeand position of the device during the full range of motion.

After insertion, the balloon can be slowly injected with, for example, aself-hardening material, or material that hardens upon activation.Suitable materials are described below and would be apparent to those ofskill in the art. Typically, upon injection, the material is in a fluidor semi-fluid state. The material expands the balloon as it is injectedwhich results in the balloon taking on the shape of the articularsurface, for example as shown in FIG. 11 A, and other articularstructures such that it fills the defect.

The balloon can be slowly injected with a self hardening or hardeningmaterial such as a polymer and even metals. The material is initially ina fluid or semi-fluid state. The material expands the balloon wherebythe shape of the balloon will take substantially the shape of thearticular surface(s) and other articular structures. The polymer willsubsequently harden inside the balloon thereby substantially taking theshape of the articular cavity and articular surface(s)/structures. Theballoon can also be composed of a bio-resorbable material. The ballooncan also be removed after the procedure.

Comparing, for example, the embodiments illustrated in FIGS. 11 A-C,FIG. 11 A illustrates a single balloon 1100 inserted between two jointsurfaces 1102, 1104 of a joint 1110. In this figure, the joint surfacesare illustrated with associated cartilage 1106, 1108. The proximal end1112 of the balloon is configured to communicate with a device thatenables the balloon to be inflated, e.g. by filling the balloon 1100with a substance. Substances include, but are not limited to, air,polymers, crystal free metals, or any other suitable material, such asthose discussed in Section II above. The balloon 1100 of FIG. 11 A isconfigured such that the distal end of the balloon 1114 does not extendbeyond distal end of the joint 1120 (where the distal end of the jointis defined relative to the area of the joint where the balloon enteredthe joint).

FIG. 11 B illustrates an alternative balloon 1130 wherein the distal end1114 of the balloon 1130 and the proximal end 1113 of the balloon 1130extends beyond the distal 1120 and proximal 1122 end of the joint. Thisextension can be optimized for flexion and extension by using differentballoon sizes. FIG. 11 C illustrates a balloon 1140 wherein the balloon1140 is configured such that the distal end 1114 of the balloon 1140extends beyond the distal 1120 of the joint while the proximal end 1114of the balloon 1140 does not extend beyond the end of the joint. As willbe appreciated by those of skill in the art, other permutations arepossible without departing from the scope of the invention.

Additionally, a sharp instrument such as a scalpel can be inserted intothe balloon or adjacent to the balloon and the balloon can be cut orslit. The balloon can then be pulled back from the hardened material andremoved from the joint, preferably through a catheter or an arthroscopyportal.

More than one balloon can be used as illustrated in FIGS. 11 D-G. Wherea plurality of balloons used, the balloons can be configured such thatthe balloons are inserted side-by-side as shown by 1150, 1152 in FIG. 11D, inserted in different compartments as shown by 1154, 1156 in FIG. 11E, one or more balloons are encompassed within the lumen of anotherballoon, as shown by 1160, 1162 and 1170, 1172, 1174 in FIGS. 11 F-G, ina top-bottom relationship, and/or combinations thereof.

Each balloon can have the same or different wall thickness or can becomposed of the same or different materials. As a result of differencesin material, a person of skill in the art will appreciate that theamount of pressure required to expand each of the balloons can varyeither uniformly or in a non-uniform fashion. These pressures would beknown to a person of skill in the art and are not discussed at lengthherein to avoid obscuring the invention.

For example, in one scenario the superior and inferior surface of afirst, inner balloon, can have a low inflation pressure relative to asecond balloon. Thus, as the material is injected, the pressure createdinside the lumen of the balloon is directly transmitted to one or morearticular surface. In this manner, the distance between the twoarticular surfaces can be controlled and a minimum distance can beobtained ensuring a sufficient thickness of the resultant implant. Thisembodiment can be useful in areas within or bordering the contact zoneof the articular surface.

A second outer or peripheral balloon can be provided that requires ahigher inflation pressure relative to the first balloon. The inner, lowinflation pressure balloon can be placed in the weight-bearing zone. Thesame balloon can also have different wall properties in differentregions of the balloon, e.g. a rigid wall with high inflation pressuresin the periphery and a less rigid wall with intermediate or lowinflation pressures in the center.

Alternatively, a first balloon, having a low inflation pressure relativeto a second balloon is provided in an area bordering the contact zone ofthe articular surface. Again, as material is injected, the pressurecreated inside the lumen of the balloon is directly transmitted to oneor more articular surface. In this manner, the distance between the twoarticular surfaces can be controlled and a minimum distance can beobtained ensuring a sufficient thickness of the resultant implant.

A second balloon can be provided at an area where there is relativelymore weight bearing. This balloon can be configured to require a higherinflation pressure relative to the first balloon.

Differences in wall thickness, pressure tolerances and expandability ofballoons can also be used to influence the resulting shape of theinjected material.

The results of using inflation devices, or balloons, with differing wallthicknesses or pressure tolerances is shown in FIGS. 12 A-F. As shown inFIG. 12 A the balloon 1200 has an upper surface 1210 and a lower surface1212 along with a proximal end 1214 and a distal end 1216. The relativepressure tolerance of the balloon or inflation device 1200 is lower onthe lower surface 1212 than the upper surface 1210. As a result, theupper surface of the balloon 1210 has a relatively flat configurationrelative to its corresponding joint surface while the lower surface 1212has a relatively conforming shape relative to its corresponding jointsurface.

Turning now to FIG. 12 B, the inflation device used 1220 has arelatively constant pressure tolerance that is relatively high whichresults in both the upper surface 1210 and the lower surface 1212 havingrelatively flat configurations relative to each of its correspondingjoint surfaces, regardless of the joint surface anatomy.

FIG. 12 C illustrates a balloon 1230 having a low inflation pressure atits proximal 1214 and distal 1216 ends, with a higher inflation pressureat a central region 1218. The result of this configuration is that whenthe balloon is inflated, the proximal and distal ends inflate to agreater profile (e.g., height) than the central region. The inflationpressure of the central region, although higher than the proximal anddistal ends, can be set such that the central region has a relativelyflat configuration relative to the corresponding joint surfaces, asshown, or can be configured to achieve the result shown in FIG. 12 A.

As will be appreciated by those of skill in the art, any of theseballoons can be configured to have varying properties resulting inportions of the wall being less rigid than other portions, within thesame balloon, e.g. a rigid wall with high inflation pressures in theperiphery and a less rigid wall with intermediate or low inflationpressures in the center. Where there is more than one thickness to theballoon, it could, for example, have less stiffness anteriorly; greaterstiffness centrally, and less stiffness posteriorly. The wall thicknessvariability will enable the device to accommodate shape formation.Central thickness will help prevent the device from fully conforming tothe irregular surface of the joint, which may be important where thereare irregularities to the joint surface, such as bone spurs.Alternatively, if the central portion is of less stiffness than theanterior and posterior sections, the device would be configured toconform more closely to the shape of the joint surface, including anyirregularities. The closer the device conforms to the joint shape, themore the device seats within the joint.

Optionally, the surgeon can elect to remove surface irregularities,including bone spurs. This can be done using known techniques such asarthroscopy or open arthrotomy.

Where more than one balloon is used, the different balloons can havedifferent shapes and sizes. Shape and size can be adjusted or selectedfor a given patient and joint. In addition to size and shape differencesof the balloons, each of the balloons can also be configured to havedifferent and/or varying wall thicknesses. For example, one ballooncould be configured with a central portion that is less stiff than theanterior and posterior sections while a second balloon could beconfigured so that the central portion is of greater stiffness than theanterior and posterior section.

FIGS. 12 D-E illustrate configurations using two balloons. As shown inFIG. 12 D the first balloon 1244 sits within a second balloon 1242 toform an inflation device 1240. In this embodiment, the inferior surface1246 of the external second balloon 1242 is configured with an inflationpressure that enables at least one surface of the device to conform, orsubstantially conform, to the corresponding joint surface. FIG. 12 Ealso illustrates a two balloon configuration 1250 with a first balloon1254 and a second balloon 1252. In this embodiment, the inflationpressure of the device is configured such that the surface does notsubstantially conform to the corresponding joint surface.

FIGS. 13 A-J(1-3) illustrate a variety of cross-sections possible forthe embodiments shown in FIGS. 11-12. These embodiments illustratepossible profiles achieved with a single balloon (FIGS. 13 A(1-3)); adual balloon embodiment wherein one balloon fits within a second balloonin approximately a central position (FIG. 13 B(1-3)) or in anoff-centered position within a second balloon (FIGS. 13 D(1-3)); atri-balloon set-up where two balloons fit within a first balloon (FIGS.13 C(1-3)), three balloons are positioned next to each other (FIGS. 13H(1-3)), or two balloons are adjacent each other while one balloon hasanother balloon within its lumen (FIGS. 13 E(2-3), F(2), G(2)); a fourballoon set-up where two balloons are adjacent each other and each onehas a balloon within its lumen (FIG. 13 G(3)) or three balloons areadjacent each other with at least one of the three balloons havinganother balloon within its lumen (FIGS. 13 I(2-3)), or a five balloonset up where three balloons are positioned adjacent each other and twoof the three balloons have balloons within its lumen (FIG. 13 J(1)). Aswill be appreciated by those of skill in the art, other combinations andprofiles are achievable using the teachings of the invention withoutdeparting from the scope of the invention. All possible combinationshave not been illustrated in order to avoid obscuring the invention.

In another embodiment, a probe can be inserted into the balloon or thedevice. The probe can be utilized for measuring the device thickness(e.g. minima and maxima). In this and other embodiments, the balloon canbe initially injected with a test material that is typically nothardening. Once inside the balloon or the device, the thickness of thedevice or the balloon can be measured, e.g. for a given inflationpressure. In this manner, a sufficient minimum implant thickness can beensured. Probes to measure the thickness of the device or the ballooninclude, but are not limited to ultrasound, including A-, B- or C-scan.

Turning now to FIGS. 14 A-J which illustrate the cartilage repair systemdescribed in FIG. 10 B utilizing the retaining device. FIGS. 14 A and Dillustrate a cartilage defect 1501 on an articular surface 1500 in thesagittal plane S and the coronal plane C. The surgeon debrides thedefect thereby optionally creating smooth margins 1502.

A retaining device 1510 is applied to the defect 1501 to define a cavity1520. A hardening material can be injected into an aperture 1512 in theretaining device 1510. Suitable materials include, but not limited to, apolymer or a crystal free metal. Additionally, as will be appreciated bythose of skill in the art, the material injected can be initially inpowder form with a liquid catalyst or hardening material injectedthereafter.

As illustrated in FIGS. 14 G, the surface of the bone 1550 can beprepared, e.g. by curette or drill, so that the surface of the bone 1550defines small teeth, holes, or anchoring members, 1552 that help anchorthe resulting device to the articular surface 1550. As shown in FIGS. 14G(2) and (5) the drill holes can be drilled parallel in relation to oneanother, where there are more than two, and perpendicular to the surfaceof the subchondral bone 1552. Alternatively, the drill holes can bedrilled at an angle in relationship to each other and at a angle that isnot perpendicular to the subchondral bone 1553 as illustrated in FIG. 15G(3-4). As will be appreciated by those of skill in the art, one or morepegs can be created on the surface of the bone. For example FIG. 14 G(2)illustrates a two peg set-up while FIG. 14 G(8) illustrates a single pegscenario and FIG. 14 G(4) illustrates a four peg scenario where somepegs are in parallel relationship while others are not. As shown in FIG.14 G(9), the aperture (1552 or 1553) can be formed so that the bore doesnot form a cylinder, but rather has channel protrusions 1572 into thebone that, when filled, form the turning channel for a screw, thusresulting in the filled aperture forming a screw that enables theanchored device to be removed by turning in a clockwise orcounter-clockwise direction.

As shown in FIG. 14 H, a ridge 1546, typically circumferential, can beused. The circumferential ridge can help achieve a tight seal betweenthe detaining device and the cartilage in order to avoid spillage of theinjected material in the joint cavity. Alternatively, the periphery ofthe mold can include a soft, compressible material that helps achieve atight seal between the mold and the surrounding cartilage.

FIG. 14 I illustrates the retaining mold with a handle placed on thesurface of a bone.

As shown in FIG. 14 J, the retaining device 1510 can have one or morehandles 1547 attached to it. The handle can facilitate the surgeonmaintaining the retaining device in position while the injected materialhardens. The aperture 1512 of the retaining device accepts injectionsand can include a membrane 1513 as shown in FIG. 14 J. The configurationassists in creating a tight seal after a needle 1560 or injectioninstrument used to inject the material 1570 into the cavity 1520 isremoved. Additionally, or inplace of the membrane 1513, a cap 1514 canbe provided that seals the aperture 1512 after the material 1570 isinjected. Additionally, anchoring teeth 1590 can be provided thatcommunicate with the meniscus 1591 or cartilage surrounding a defect.The anchoring teeth 1590 help keep the device stable when placed overthe defect.

As illustrated in FIG. 14 G(4) more than one aperture 1512, 1512′ can beprovided without departing from the scope of the invention.

The retaining device system can be designed to inject an area equal toor slightly greater than the area of diseased cartilage. Alternatively,the retaining device system can be designed for the entireweight-bearing surface or the entire articular surface of a compartment.Retaining devices can be used on opposing articular surfaces, e.g. on afemoral condyle and a tibial plateau, thereby recreating a smoothgliding surface on both articular surfaces.

The retaining device can be designed to allow for light exposureincluding UV light. For example, the retaining device can be made usinga transparent plastic. The retaining device can also be made to allowfor passage of ultrasound waves.

C. Customized Containers

In another embodiment of the invention, a container or well can beformed to the selected specifications, for example to match the materialneeded for a particular subject or to create a stock of repair materialsin a variety of sizes. The size and shape of the container can bedesigned using the thickness and curvature information obtained from thejoint and from the cartilage defect. More specifically, the inside ofthe container can be shaped to follow any selected measurements, forexample as obtained from the cartilage defect(s) of a particularsubject. The container can be filled with a cartilage replacement orregenerating material, for example, collagen-containing materials,plastics, bioresorbable materials and/or any suitable tissue scaffold.The cartilage regenerating or replacement material can also consist of asuspension of stem cells or fetal or immature or mature cartilage cellsthat subsequently develop to more mature cartilage inside the container.Further, development and/or differentiation can be enhanced with use ofcertain tissue nutrients and growth factors.

The material is allowed to harden and/or grow inside the container untilthe material has the desired traits, for example, thickness, elasticity,hardness, biochemical composition, etc. Molds can be generated using anysuitable technique, for example computer devices and automation, e.g.computer assisted design (CAD) and, for example, computer assistedmodeling (CAM). Because the resulting material generally follows thecontour of the inside of the container it will better fit the defectitself and facilitate integration.

D. Designs Encompassing Multiple Component Repair Materials

The articular repair system or implants described herein can include oneor more components.

FIGS. 15 A-B shows single and multiple component devices. FIG. 15 Aillustrates an example of a single component articular surface repairsystem 1400 with varying curvature and radii that fits within thesubchondral bone 1420 such that the interior surface 1402 of the system1400 does not form an extension of the surface of the subchondral bone1422. The articular surface repair system is chosen to include convex1402 and concave 1404 portions. Such devices can be preferable in alateral femoral condyle or small joints such as the elbow joint. FIG. 15B depicts a multi-component articular surface repair system with asecond component 1410 with a surface 1412 that forms an extension of thesurface 1422 of the subchondral bone 1420 and a first component 1405with an interior surface 1406 that forms an extension of the curvatureand shape of the surrounding normal cartilage 1415. The second component1410 and the first component 1405 demonstrate varying curvatures andradii with convex and concave portions that correspond to the curvatureof the subchondral bone 1420 and/or the normal cartilage 1415. As willbe appreciated by those of skill in the art, these two components can beformed such that the parts are integrally formed with each other, or canbe formed such that each part abuts the other. Additionally, therelationship between the parts can be by any suitable mechanismincluding adhesives and mechanical means.

FIGS. 16 A-B show articular repair systems 100 having an outer contour102 forming an extension of the surrounding normal cartilage 200. Thesystems are implanted into the underlying bone 300 using one or morepegs 150, 175. The pegs, pins, or screws can be porous-coated and canhave flanges 125 as shown in FIG. 15 B.

FIG. 17 shows an exemplary articular repair device 500 including a flatsurface 510 to control depth and prevent toggle; an exterior surface 515having the contour of normal cartilage; flanges 517 to prevent rotationand control toggle; a groove 520 to facilitate tissue in-growth.

FIGS. 18 A-D depict, in cross-section, another example of an implant 640with multiple anchoring pegs, stems, or screws 645. FIG. 18 B-D showvarious cross-sectional representations of various possible embodimentsof the pegs, or anchoring stems. FIG. 18 B shows a peg 645 having anotch 646 or groove around its circumference; FIG. 18 C shows a peg 645with radially-extending arms 647 that help anchor the device in theunderlying bone; and FIG. 18 D shows a peg 645 with multiple grooves orflanges 648.

FIGS. 19 A-B depict an overhead view of an exemplary implant 650 withmultiple anchoring pegs 655 which illustrates that the pegs are notnecessarily linearly aligned along the longitudinal axis of the device.

FIG. 20 A depicts an implant 660 with a peg 661 having radiallyextending arms 665. FIGS. 20 B-E are top views of the implant pegsillustrating a variety of suitable alternative shapes.

Examples of one-component systems include, but are not limited to, aplastic, a polymer, a metal, a metal alloy, crystal free metals, abiologic material or combinations thereof. In certain embodiments, thesurface of the repair system facing the underlying bone can be smooth.In other embodiments, the surface of the repair system facing theunderlying bone can be porous or porous-coated. In another aspect, thesurface of the repair system facing the underlying bone is designed withone or more grooves, for example to facilitate the in-growth of thesurrounding tissue. The external surface of the device can have astep-like design, which can be advantageous for altering biomechanicalstresses. Optionally, flanges can also be added at one or more positionson the device (e.g., to prevent the repair system from rotating, tocontrol toggle and/or prevent settling into the marrow cavity). Theflanges can be part of a conical or a cylindrical design. A portion orall of the repair system facing the underlying bone can also be flatwhich can help to control depth of the implant and to prevent toggle.

Non-limiting examples of multiple-component systems include combinationsof metal, plastic, metal alloys, crystal free metals, and one or morebiological materials. One or more components of the articular surfacerepair system can be composed of a biologic material (e.g. a tissuescaffold with cells such as cartilage cells or stem cells alone orseeded within a substrate such as a bioresorable material or a tissuescaffold, allograft, autograft or combinations thereof) and/or anon-biological material (e.g., polyethylene or a chromium alloy such aschromium cobalt).

Thus, the repair system can include one or more areas of a singlematerial or a combination of materials, for example, the articularsurface repair system can have a first and a second component. The firstcomponent is typically designed to have size, thickness and curvaturesimilar to that of the cartilage tissue lost while the second componentis typically designed to have a curvature similar to the subchondralbone. In addition, the first component can have biomechanical propertiessimilar to articular cartilage, including but not limited to similarelasticity and resistance to axial loading or shear forces. The firstand the second component can consist of two different metals or metalalloys. One or more components of the system (e.g., the second portion)can be composed of a biologic material including, but not limited tobone, or a non-biologic material including, but not limited tohydroxyapatite, tantalum, a chromium alloy, chromium cobalt or othermetal alloys.

One or more regions of the articular surface repair system (e.g., theouter margin of the first portion and/or the second portion) can bebioresorbable, for example to allow the interface between the articularsurface repair system and the patient's normal cartilage, over time, tobe filled in with hyaline or fibrocartilage. Similarly, one or moreregions (e.g., the outer margin of the first portion of the articularsurface repair system and/or the second portion) can be porous. Thedegree of porosity can change throughout the porous region, linearly ornon-linearly, for where the degree of porosity will typically decreasetowards the center of the articular surface repair system. The pores canbe designed for in-growth of cartilage cells, cartilage matrix, andconnective tissue thereby achieving a smooth interface between thearticular surface repair system and the surrounding cartilage.

The repair system (e.g., the second component in multiple componentsystems) can be attached to the patient's bone with use of a cement-likematerial such as methylmethacrylate, injectable hydroxy- orcalcium-apatite materials and the like.

In certain embodiments, one or more portions of the articular surfacerepair system can be pliable or liquid or deformable at the time ofimplantation and can harden later. Hardening can occur, for example,within 1 second to 2 hours (or any time period therebetween), preferablywith in 1 second to 30 minutes (or any time period therebetween), morepreferably between 1 second and 10 minutes (or any time periodtherebetween).

One or more components of the articular surface repair system can beadapted to receive injections. For example, the external surface of thearticular surface repair system can have one or more openings therein.The openings can be sized to receive screws, tubing, needles or otherdevices which can be inserted and advanced to the desired depth, forexample, through the articular surface repair system into the marrowspace. Injectables such as methylmethacrylate and injectable hydroxy- orcalcium-apatite materials can then be introduced through the opening (ortubing inserted therethrough) into the marrow space thereby bonding thearticular surface repair system with the marrow space. Similarly, screwsor pins, or other anchoring mechanisms. can be inserted into theopenings and advanced to the underlying subchondral bone and the bonemarrow or epiphysis to achieve fixation of the articular surface repairsystem to the bone. Portions or all components of the screw or pin canbe bioresorbable, for example, the distal portion of a screw thatprotrudes into the marrow space can be bioresorbable. During the initialperiod after the surgery, the screw can provide the primary fixation ofthe articular surface repair system. Subsequently, ingrowth of bone intoa porous coated area along the undersurface of the articular cartilagerepair system can take over as the primary stabilizer of the articularsurface repair system against the bone.

The articular surface repair system can be anchored to the patient'sbone with use of a pin or screw or other attachment mechanism. Theattachment mechanism can be bioresorbable. The screw or pin orattachment mechanism can be inserted and advanced towards the articularsurface repair system from a non-cartilage covered portion of the boneor from a non-weight-bearing surface of the joint.

The interface between the articular surface repair system and thesurrounding normal cartilage can be at an angle, for example oriented atan angle of 90 degrees relative to the underlying subchondral bone.Suitable angles can be determined in view of the teachings herein, andin certain cases, non-90 degree angles can have advantages with regardto load distribution along the interface between the articular surfacerepair system and the surrounding normal cartilage.

The interface between the articular surface repair system and thesurrounding normal cartilage and/or bone can be covered with apharmaceutical or bioactive agent, for example a material thatstimulates the biological integration of the repair system into thenormal cartilage and/or bone. The surface area of the interface can beirregular, for example, to increase exposure of the interface topharmaceutical or bioactive agents.

E. Pre-Existing Repair Systems

As described herein, repair systems, including surgical instruments,guides and molds, of various sizes, curvatures and thicknesses can beobtained. These repair systems, including surgical instruments, guidesand molds, can be catalogued and stored to create a library of systemsfrom which an appropriate system for an individual patient can then beselected. In other words, a defect, or an articular surface, is assessedin a particular subject and a pre-existing repair system, includingsurgical instruments, guides and molds, having a suitable shape and sizeis selected from the library for further manipulation (e.g., shaping)and implantation.

F. Mini-Prosthesis

As noted above, the methods and compositions described herein can beused to replace only a portion of the articular surface, for example, anarea of diseased cartilage or lost cartilage on the articular surface.In these systems, the articular surface repair system can be designed toreplace only the area of diseased or lost cartilage or it can extendbeyond the area of diseased or lost cartilage, e.g., 3 or 5 mm intonormal adjacent cartilage. In certain embodiments, the prosthesisreplaces less than about 70% to 80% (or any value therebetween) of thearticular surface (e.g., any given articular surface such as a singlefemoral condyle, etc.), preferably, less than about 50% to 70% (or anyvalue therebetween), more preferably, less than about 30% to 50% (or anyvalue therebetween), more preferably less than about 20% to 30% (or anyvalue therebetween), even more preferably less than about 20% of thearticular surface.

The prosthesis can include multiple components, for example a componentthat is implanted into the bone (e.g., a metallic device) attached to acomponent that is shaped to cover the defect of the cartilage overlayingthe bone. Additional components, for example intermediate plates,meniscal repair systems and the like can also be included. It iscontemplated that each component replaces less than all of thecorresponding articular surface. However, each component need notreplace the same portion of the articular surface. In other words, theprosthesis can have a bone-implanted component that replaces less than30% of the bone and a cartilage component that replaces 60% of thecartilage. The prosthesis can include any combination, provided eachcomponent replaces less than the entire articular surface.

The articular surface repair system can be formed or selected so that itwill achieve a near anatomic fit or match with the surrounding oradjacent cartilage. Typically, the articular surface repair system isformed and/or selected so that its outer margin located at the externalsurface will be aligned with the surrounding or adjacent cartilage.

Thus, the articular repair system can be designed to replace theweight-bearing portion (or more or less than the weight bearing portion)of an articular surface, for example in a femoral condyle. Theweight-bearing surface refers to the contact area between two opposingarticular surfaces during activities of normal daily living (e.g.,normal gait). At least one or more weight-bearing portions can bereplaced in this manner, e.g., on a femoral condyle and on a tibia.

In other embodiments, an area of diseased cartilage or cartilage losscan be identified in a weight-bearing area and only a portion of theweight-bearing area, specifically the portion containing the diseasedcartilage or area of cartilage loss, can be replaced with an articularsurface repair system.

In another embodiment, the articular repair system can be designed orselected to replace substantially all of the articular surface, e.g. acondyle.

In another embodiment, for example, in patients with diffuse cartilageloss, the articular repair system can be designed to replace an areaslightly larger than the weight-bearing surface.

In certain aspects, the defect to be repaired is located only on onearticular surface, typically the most diseased surface. For example, ina patient with severe cartilage loss in the medial femoral condyle butless severe disease in the tibia, the articular surface repair systemcan only be applied to the medial femoral condyle. Preferably, in anymethods described herein, the articular surface repair system isdesigned to achieve an exact or a near anatomic fit with the adjacentnormal cartilage.

In other embodiments, more than one articular surface can be repaired.The area(s) of repair will be typically limited to areas of diseasedcartilage or cartilage loss or areas slightly greater than the area ofdiseased cartilage or cartilage loss within the weight-bearingsurface(s).

The implant and/or the implant site can be sculpted to achieve a nearanatomic alignment between the implant and the implant site. In anotherembodiment of the invention, an electronic image is used to measure thethickness, curvature, or shape of the articular cartilage or thesubchondral bone, and/or the size of a defect, and an articular surfacerepair system is selected using this information. The articular surfacerepair system can be inserted arthroscopically. The articular surfacerepair system can have a single radius. More typically, however, asshown in FIG. 15 A, discussed above, the articular surface repair system1500 has varying curvatures and radii within the same plane, e.g.anteroposterior or mediolateral or superoinferior or oblique planes, orwithin multiple planes. In this manner, the articular surface repairsystem can be shaped to achieve a near anatomic alignment between theimplant and the implant site. This design allows not only allows fordifferent degrees of convexity or concavity, but also for concaveportions within a predominantly convex shape or vice versa 1500.

In another embodiment the articular surface repair system has ananchoring stem, used to anchor the device, for example, as described inU.S. Pat. No. 6,224,632 to Pappas et al issued May 1, 2001. The stem, orpeg, can have different shapes including conical, rectangular, fin amongothers. The mating bone cavity is typically similarly shaped as thecorresponding stem.

As shown in FIG. 16, discussed above, the articular surface repairsystem 100 can be affixed to the subchondral bone 300, with one or morestems, or pegs, 150 extending through the subchondral plate into themarrow space. In certain instances, this design can reduce thelikelihood that the implant will settle deeper into the joint over timeby resting portions of the implant against the subchondral bone. Thestems, or pegs, can be of any shape suitable to perform the function ofanchoring the device to the bone. For example, the pegs can becylindrical or conical. Optionally, the stems, or pegs, can furtherinclude notches or openings to allow bone in-growth. In addition, thestems can be porous coated for bone in-growth. The anchoring stems orpegs can be affixed to the bone using bone cement. An additionalanchoring device can also be affixed to the stem or peg. The anchoringdevice can have an umbrella shape (e.g., radially expanding elements)with the wider portion pointing towards the subchondral bone and awayfrom the peg. The anchoring device can be advantageous for providingimmediate fixation of the implant. The undersurface of the articularrepair system facing the subchondral bone can be textured or roughthereby increasing the contact surface between the articular repairsystem and the subchondral bone. Alternatively, the undersurface of thearticular repair system can be porous coated thereby allowing in-growth.The surgeon can support the in-growth of bone by treating thesubchondral bone with a rasp, typically to create a larger surface areaand/or until bleeding from the subchondral bone occurs.

In another embodiment, the articular surface repair system can beattached to the underlying bone or bone marrow using bone cement. Bonecement is typically made from an acrylic polymeric material. Typically,the bone cement is comprised of two components: a dry powder componentand a liquid component, which are subsequently mixed together. The drycomponent generally includes an acrylic polymer, such aspolymethylmethacrylate (PMMA). The dry component can also contain apolymerization initiator such as benzoylperoxide, which initiates thefree-radical polymerization process that occurs when the bone cement isformed. The liquid component, on the other hand, generally contains aliquid monomer such as methyl methacrylate (MMA). The liquid componentcan also contain an accelerator such as an amine (e.g.,N,N-dimethyl-p-toluidine). A stabilizer, such as hydroquinone, can alsobe added to the liquid component to prevent premature polymerization ofthe liquid monomer. When the liquid component is mixed with the drycomponent, the dry component begins to dissolve or swell in the liquidmonomer. The amine accelerator reacts with the initiator to form freeradicals that begin to link monomer units to form polymer chains. In thenext two to four minutes, the polymerization process proceeds changingthe viscosity of the mixture from a syrup-like consistency (lowviscosity) into a dough-like consistency (high viscosity). Ultimately,further polymerization and curing occur, causing the cement to hardenand affix a prosthesis to a bone.

In certain aspects of the invention, as shown in FIG. 7 E, above, bonecement 755 or another liquid attachment material such as injectablecalciumhydroxyapatite can be injected into the marrow cavity through oneor more openings 750 in the prosthesis. These openings in the prosthesiscan extend from the articular surface to the undersurface of theprosthesis 760. After injection, the openings can be closed with apolymer, silicon, metal, metal alloy or bioresorbable plug.

In another embodiment, one or more components of the articular surfacerepair (e.g., the surface of the system that is pointing towards theunderlying bone or bone marrow) can be porous or porous coated. Avariety of different porous metal coatings have been proposed forenhancing fixation of a metallic prosthesis by bone tissue in-growth.Thus, for example, U.S. Pat. No. 3,855,638 to Pilliar issued Dec. 24,2974, discloses a surgical prosthetic device, which can be used as abone prosthesis, comprising a composite structure consisting of a solidmetallic material substrate and a porous coating of the same solidmetallic material adhered to and extending over at least a portion ofthe surface of the substrate. The porous coating consists of a pluralityof small discrete particles of metallic material bonded together attheir points of contact with each other to define a plurality ofconnected interstitial pores in the coating. The size and spacing of theparticles, which can be distributed in a plurality of monolayers, can besuch that the average interstitial pore size is not more than about 200microns. Additionally, the pore size distribution can be substantiallyuniform from the substrate-coating interface to the surface of thecoating. In another embodiment, the articular surface repair system cancontain one or more polymeric materials that can be loaded with andrelease therapeutic agents including drugs or other pharmacologicaltreatments that can be used for drug delivery. The polymeric materialscan, for example, be placed inside areas of porous coating. Thepolymeric materials can be used to release therapeutic drugs, e.g. boneor cartilage growth stimulating drugs. This embodiment can be combinedwith other embodiments, wherein portions of the articular surface repairsystem can be bioresorbable. For example, the first layer of anarticular surface repair system or portions of its first layer can bebioresorbable. As the first layer gets increasingly resorbed, localrelease of a cartilage growth-stimulating drug can facilitate in-growthof cartilage cells and matrix formation.

In any of the methods or compositions described herein, the articularsurface repair system can be pre-manufactured with a range of sizes,curvatures and thicknesses. Alternatively, the articular surface repairsystem can be custom-made for an individual patient.

IV. Manufacturing

A. Shaping

In certain instances shaping of the repair material will be requiredbefore or after formation (e.g., growth to desired thickness), forexample where the thickness of the required cartilage material is notuniform (e.g., where different sections of the cartilage replacement orregenerating material require different thicknesses).

The replacement material can be shaped by any suitable techniqueincluding, but not limited to, mechanical abrasion, laser abrasion orablation, radiofrequency treatment, cryoablation, variations in exposuretime and concentration of nutrients, enzymes or growth factors and anyother means suitable for influencing or changing cartilage thickness.See, e.g., WO 00/15153 to Mansmann published Mar. 23, 2000; If enzymaticdigestion is used, certain sections of the cartilage replacement orregenerating material can be exposed to higher doses of the enzyme orcan be exposed longer as a means of achieving different thicknesses andcurvatures of the cartilage replacement or regenerating material indifferent sections of said material.

The material can be shaped manually and/or automatically, for exampleusing a device into which a pre-selected thickness and/or curvature hasbeen input and then programming the device using the input informationto achieve the desired shape.

In addition to, or instead of, shaping the cartilage repair material,the site of implantation (e.g., bone surface, any cartilage materialremaining, etc.) can also be shaped by any suitable technique in orderto enhance integration of the repair material.

B. Sizing

The articular repair system can be formed or selected so that it willachieve a near anatomic fit or match with the surrounding or adjacentcartilage or subchondral bone or menisci and other tissue. The shape ofthe repair system can be based on the analysis of an electronic image(e.g. MRI, CT, digital tomosynthesis, optical coherence tomography orthe like). If the articular repair system is intended to replace an areaof diseased cartilage or lost cartilage, the near anatomic fit can beachieved using a method that provides a virtual reconstruction of theshape of healthy cartilage in an electronic image.

In one embodiment of the invention, a near normal cartilage surface atthe position of the cartilage defect can be reconstructed byinterpolating the healthy cartilage surface across the cartilage defector area of diseased cartilage. This can, for example, be achieved bydescribing the healthy cartilage by means of a parametric surface (e.g.a B-spline surface), for which the control points are placed such thatthe parametric surface follows the contour of the healthy cartilage andbridges the cartilage defect or area of diseased cartilage. Thecontinuity properties of the parametric surface will provide a smoothintegration of the part that bridges the cartilage defect or area ofdiseased cartilage with the contour of the surrounding healthycartilage. The part of the parametric surface over the area of thecartilage defect or area of diseased cartilage can be used to determinethe shape or part of the shape of the articular repair system to matchwith the surrounding cartilage.

In another embodiment, a near normal cartilage surface at the positionof the cartilage defect or area of diseased cartilage can bereconstructed using morphological image processing. In a first step, thecartilage can be extracted from the electronic image using manual,semi-automated and/or automated segmentation techniques (e.g., manualtracing, region growing, live wire, model-based segmentation), resultingin a binary image. Defects in the cartilage appear as indentations thatcan be filled with a morphological closing operation performed in 2-D or3-D with an appropriately selected structuring element. The closingoperation is typically defined as a dilation followed by an erosion. Adilation operator sets the current pixel in the output image to 1 if atleast one pixel of the structuring element lies inside a region in thesource image. An erosion operator sets the current pixel in the outputimage to 1 if the whole structuring element lies inside a region in thesource image. The filling of the cartilage defect or area of diseasedcartilage creates a new surface over the area of the cartilage defect orarea of diseased cartilage that can be used to determine the shape orpart of the shape of the articular repair system to match with thesurrounding cartilage or subchondral bone.

As described above, the articular repair system, including surgicaltools and instruments, molds, in situ repair systems, etc. can be formedor selected from a library or database of systems of various sizes,curvatures and thicknesses so that it will achieve a near anatomic fitor match with the surrounding or adjacent cartilage and/or subchondralbone. These systems can be pre-made or made to order for an individualpatient. In order to control the fit or match of the articular repairsystem with the surrounding or adjacent cartilage or subchondral bone ormenisci and other tissues preoperatively, a software program can be usedthat projects the articular repair system over the anatomic positionwhere it will be implanted. Suitable software is commercially availableand/or readily modified or designed by a skilled programmer.

In yet another embodiment, the articular surface repair system can beprojected over the implantation site using one or more 3-D images. Thecartilage and/or subchondral bone and other anatomic structures areextracted from a 3-D electronic image such as an MRI or a CT usingmanual, semi-automated and/or automated segmentation techniques. A 3-Drepresentation of the cartilage and/or subchondral bone and otheranatomic structures as well as the articular repair system is generated,for example using a polygon or NURBS surface or other parametric surfacerepresentation. For a description of various parametric surfacerepresentations see, for example Foley, J. D. et al., Computer Graphics:Principles and Practice in C; Addison-Wesley, 2^(nd) edition, 1995).

The 3-D representations of the cartilage and/or subchondral bone andother anatomic structures and the articular repair system can be mergedinto a common coordinate system. The articular repair system, includingsurgical tools and instruments, molds, in situ repair systems, etc. canthen be placed at the desired implantation site. The representations ofthe cartilage, subchondral bone, menisci and other anatomic structuresand the articular repair system are rendered into a 3-D image, forexample application programming interfaces (APIs) OpenGL® (standardlibrary of advanced 3-D graphics functions developed by SGI, Inc.;available as part of the drivers for PC-based video cards, for examplefrom www.nvidia.com for NVIDIA video cards or www.3dlabs.com for 3Dlabsproducts, or as part of the system software for Unix workstations) orDirectX® (multimedia API for Microsoft Windows® based PC systems;available from www.microsoft.com). The 3-D image can be rendered showingthe cartilage, subchondral bone, menisci or other anatomic objects, andthe articular repair system from varying angles, e.g. by rotating ormoving them interactively or non-interactively, in real-time ornon-real-time.

The software can be designed so that the articular repair system,including surgical tools and instruments, molds, in situ repair systems,etc. with the best fit relative to the cartilage and/or subchondral boneis automatically selected, for example using some of the techniquesdescribed above. Alternatively, the operator can select an articularrepair system, including surgical tools and instruments, molds, in siturepair systems, etc. and project it or drag it onto the implantationsite using suitable tools and techniques. The operator can move androtate the articular repair systems in three dimensions relative to theimplantation site and can perform a visual inspection of the fit betweenthe articular repair system and the implantation site. The visualinspection can be computer assisted. The procedure can be repeated untila satisfactory fit has been achieved. The procedure can be performedmanually by the operator; or it can be computer-assisted in whole orpart. For example, the software can select a first trial implant thatthe operator can test. The operator can evaluate the fit. The softwarecan be designed and used to highlight areas of poor alignment betweenthe implant and the surrounding cartilage or subchondral bone or meniscior other tissues. Based on this information, the software or theoperator can then select another implant and test its alignment. One ofskill in the art will readily be able to select, modify and/or createsuitable computer programs for the purposes described herein.

In another embodiment, the implantation site can be visualized using oneor more cross-sectional 2-D images. Typically, a series of 2-Dcross-sectional images will be used. The 2-D images can be generatedwith imaging tests such as CT, MRI, digital tomosynthesis, ultrasound,or optical coherence tomography using methods and tools known to thoseof skill in the art. The articular repair system, including surgicaltools and instruments, molds, in situ repair systems, etc. can then besuperimposed onto one or more of these 2-D images. The 2-Dcross-sectional images can be reconstructed in other planes, e.g. fromsagittal to coronal, etc. Isotropic data sets (e.g., data sets where theslice thickness is the same or nearly the same as the in-planeresolution) or near isotropic data sets can also be used. Multipleplanes can be displayed simultaneously, for example using a split screendisplay. The operator can also scroll through the 2-D images in anydesired orientation in real time or near real time; the operator canrotate the imaged tissue volume while doing this. The articular repairsystem, including surgical tools and instruments, molds, in situ repairsystems, etc. can be displayed in cross-section utilizing differentdisplay planes, e.g. sagittal, coronal or axial, typically matchingthose of the 2-D images demonstrating the cartilage, subchondral bone,menisci or other tissue. Alternatively, a three-dimensional display canbe used for the articular repair system. The 2-D electronic image andthe 2-D or 3-D representation of the articular repair system, includingsurgical tools and instruments, molds, in situ repair systems, etc. canbe merged into a common coordinate system. The articular repair systemcan then be placed at the desired implantation site. The series of 2-Dcross-sections of the anatomic structures, the implantation site and thearticular repair system can be displayed interactively (e.g. theoperator can scroll through a series of slices) or non-interactively(e.g. as an animation that moves through the series of slices), inreal-time or non-real-time.

The software can be designed so that the articular repair system,including surgical tools and instruments, molds, in situ repair systems,etc. with the best fit relative to the cartilage and/or subchondral boneis automatically selected, for example using one or more of thetechniques described above. Alternatively, the operator can select anarticular repair system, including surgical tools and instruments,molds, in situ repair systems, etc. and project it or drag it onto theimplantation site displayed on the cross-sectional 2-D images. Theoperator can then move and rotate the articular repair system relativeto the implantation site and scroll through a cross-sectional 2-Ddisplay of the articular repair system and of the anatomic structures.The operator can perform a visual and/or computer-assisted inspection ofthe fit between the articular repair system and the implantation site.The procedure can be repeated until a satisfactory fit has beenachieved. The procedure can be entirely manual by the operator; it can,however, also be computer-assisted. For example, the software can selecta first trial implant that the operator can test (e.g., evaluate thefit). Software that highlights areas of poor alignment between theimplant and the surrounding cartilage or subchondral bone or menisci orother tissues can also be designed and used. Based on this information,the software or the operator can select another implant and test itsalignment.

C. Rapid Prototyping

Rapid protyping is a technique for fabricating a three-dimensionalobject from a computer model of the object. A special printer is used tofabricate the prototype from a plurality of two-dimensional layers.Computer software sections the representations of the object into aplurality of distinct two-dimensional layers and then athree-dimensional printer fabricates a layer of material for each layersectioned by the software. Together the various fabricated layers formthe desired prototype. More information about rapid prototypingtechniques is available in US Patent Publication No 2002/0079601A1 toRussell et al., published Jun. 27, 2002. An advantage to using rapidprototyping is that it enables the use of free form fabricationtechniques that use toxic or potent compounds safely. These compoundscan be safely incorporated in an excipient envelope, which reducesworker exposure

A powder piston and build bed are provided. Powder includes any material(metal, plastic, etc.) that can be made into a powder or bonded with aliquid. The power is rolled from a feeder source with a spreader onto asurface of a bed. The thickness of the layer is controlled by thecomputer. The print head then deposits a binder fluid onto the powderlayer at a location where it is desired that the powder bind. Powder isagain rolled into the build bed and the process is repeated, with thebinding fluid deposition being controlled at each layer to correspond tothe three-dimensional location of the device formation. For a furtherdiscussion of this process see, for example, US Patent Publication No2003/017365A1 to Monkhouse et al. published Sep. 18, 2003.

The rapid prototyping can use the two dimensional images obtained, asdescribed above in Section I, to determine each of the two-dimensionalshapes for each of the layers of the prototyping machine. In thisscenario, each two dimensional image slice would correspond to a twodimensional prototype slide. Alternatively, the three-dimensional shapeof the defect can be determined, as described above, and then brokendown into two dimensional slices for the rapid prototyping process. Theadvantage of using the three-dimensional model is that thetwo-dimensional slices used for the rapid prototyping machine can bealong the same plane as the two-dimensional images taken or along adifferent plane altogether.

Rapid prototyping can be combined or used in conjunction with castingtechniques. For example, a shell or container with inner dimensionscorresponding to an articular repair system including surgicalinstruments, molds, alignment guides or surgical guides, can be madeusing rapid prototyping. Plastic or wax-like materials are typicallyused for this purpose. The inside of the container can subsequently becoated, for example with a ceramic, for subsequent casting. Using thisprocess, personalized casts can be generated.

Rapid prototyping can be used for producing articular repair systemsincluding surgical tools, molds, alignment guides, cut guides etc. Rapidprototyping can be performed at a manufacturing facility. Alternatively,it may be performed in the operating room after an intraoperativemeasurement has been performed.

V. Implantation

Following one or more manipulations (e.g., shaping, growth, development,etc), the cartilage replacement or regenerating material can then beimplanted into the area of the defect. Implantation can be performedwith the cartilage replacement or regenerating material still attachedto the base material or removed from the base material. Any suitablemethods and devices can be used for implantation, for example, devicesas described in U.S. Pat. Nos. 6,375,658 to Hangody et al. issued Apr.23, 2002; 6,358,253 to Torrie et al. issued Mar. 19, 2002; 6,328,765 toHardwick et al. issued Dec. 11, 2001; and International Publication WO01/19254 to Cummings et al. published Mar. 22, 2001.

In selected cartilage defects, the implantation site can be preparedwith a single cut across the articular surface, for example, as shown inFIG. 8. In this case, single 810 and multi-component 820 prostheses canbe utilized.

A. The Joint Replacement Procedure

i. Knee Joint

Performing a total knee arthroplasty is a complicated procedure. Inreplacing the knee with an artificial knee, it is important to get theanatomical and mechanical axes of the lower extremity aligned correctlyto ensure optimal functioning of the implanted knee.

As shown in FIG. 21 A, the center of the hip 1902 (located at the head1930 of the femur 1932), the center of the knee 1904 (located at thenotch where the intercondular tubercle 1934 of the tibia 1936 meet thefemur) and ankle 1906 lie approximately in a straight line 1910 whichdefines the mechanical axis of the lower extremity. The anatomic axis1920 aligns 5-7° offset θ from the mechanical axis in the valgus, oroutward, direction.

The long axis of the tibia 1936 is collinear with the mechanical axis ofthe lower extremity 1910. From a three-dimensional perspective, thelower extremity of the body ideally functions within a single planeknown as the median anterior-posterior plane (MAP-plane) throughout theflexion-extension arc. In order to accomplish this, the femoral head1930, the mechanical axis of the femur, the patellar groove, theintercondylar notch, the patellar articular crest, the tibia and theankle remain within the MAP-plane during the flexion-extension movement.During movement, the tibia rotates as the knee flexes and extends in theepicondylar axis which is perpendicular to the MAP-plane.

A variety of image slices can be taken at each individual joint, e.g.,the knee joint 1950-1950 _(n), and the hip joint 1952-1950 _(n). Theseimage slices can be used as described above in Section I along with animage of the full leg to ascertain the axis.

With disease and malfunction of the knee, alignment of the anatomic axisis altered. Performing a total knee arthroplasty is one solution forcorrecting a diseased knee. Implanting a total knee joint, such as thePFC Sigma RP Knee System by Johnson & Johnson, requires that a series ofresections be made to the surfaces forming the knee joint in order tofacilitate installation of the artificial knee. The resections should bemade to enable the installed artificial knee to achieveflexion-extension movement within the MAP-plane and to optimize thepatient's anatomical and mechanical axis of the lower extremity.

First, the tibia 1930 is resected to create a flat surface to accept thetibial component of the implant. In most cases, the tibial surface isresected perpendicular to the long axis of the tibia in the coronalplane, but is typically sloped 4-7° posteriorly in the sagittal plane tomatch the normal slope of the tibia. As will be appreciated by those ofskill in the art, the sagittal slope can be 0° where the device to beimplanted does not require a sloped tibial cut. The resection line 1958is perpendicular to the mechanical axis 1910, but the angle between theresection line and the surface plane of the plateau 1960 variesdepending on the amount of damage to the knee.

FIGS. 21 B-D illustrate an anterior view of a resection of ananatomically normal tibial component, a tibial component in a varusknee, and a tibial component in a valgus knee, respectively. In eachfigure, the mechanical axis 1910 extends vertically through the bone andthe resection line 1958 is perpendicular to the mechanical axis 1910 inthe coronal plane, varying from the surface line formed by the jointdepending on the amount of damage to the joint. FIG. 21 B illustrates anormal knee wherein the line corresponding to the surface of the joint1960 is parallel to the resection line 1958. FIG. 21 c illustrates avarus knee wherein the line corresponding to the surface of the joint1960 is not parallel to the resection line 1958. FIG. 21 D illustrates avalgus knee wherein the line corresponding to the surface of the joint1960 is not parallel to the resection line 1958.

Once the tibial surface has been prepared, the surgeon turns topreparing the femoral condyle.

The plateau of the femur 1970 is resected to provide flat surfaces thatcommunicate with the interior of the femoral prosthesis. The cuts madeto the femur are based on the overall height of the gap to be createdbetween the tibia and the femur. Typically, a 20 mm gap is desirable toprovide the implanted prosthesis adequate room to achieve full range ofmotion. The bone is resected at a 5-7° angle valgus to the mechanicalaxis of the femur. Resected surface 1972 forms a flat plane with anangular relationship to adjoining surfaces 1974, 1976. The angle θ′, θ″between the surfaces 1972-1974, and 1972-1976 varies according to thedesign of the implant.

ii. Hip Joint

As illustrated in FIG. 21 F, the external geometry of the proximal femurincludes the head 1980, the neck 1982, the lesser trochanter 1984, thegreater trochanter 1986 and the proximal femoral diaphysis. The relativepositions of the trochanters 1984, 1986, the femoral head center 1902and the femoral shaft 1988 are correlated with the inclination of theneck-shaft angle. The mechanical axis 1910 and anatomic axis 1920 arealso shown. Assessment of these relationships can change the reamingdirection to achieve neutral alignment of the prosthesis with thefemoral canal.

Using anteroposterior and lateral radiographs, measurements are made ofthe proximal and distal geometry to determine the size and optimaldesign of the implant.

Typically, after obtaining surgical access to the hip joint, the femoralneck 1982 is resected, e.g. along the line 1990. Once the neck isresected, the medullary canal is reamed. Reaming can be accomplished,for example, with a conical or straight reamer, or a flexible reamer.The depth of reaming is dictated by the specific design of the implant.Once the canal has been reamed, the proximal reamer is prepared byserial rasping, with the rasp directed down into the canal.

B. Surgical Tools

Further, surgical assistance can be provided by using a device appliedto the outer surface of the articular cartilage or the bone, includingthe subchondral bone, in order to match the alignment of the articularrepair system and the recipient site or the joint. The device can beround, circular, oval, ellipsoid, curved or irregular in shape. Theshape can be selected or adjusted to match or enclose an area ofdiseased cartilage or an area slightly larger than the area of diseasedcartilage or substantially larger than the diseased cartilage. The areacan encompass the entire articular surface or the weight bearingsurface. Such devices are typically preferred when replacement of amajority or an entire articular surface is contemplated.

Mechanical devices can be used for surgical assistance (e.g., surgicaltools), for example using gels, molds, plastics or metal. One or moreelectronic images or intraoperative measurements can be obtainedproviding object coordinates that define the articular and/or bonesurface and shape. These objects' coordinates can be utilized to eithershape the device, e.g. using a CAD/CAM technique, to be adapted to apatient's articular anatomy or, alternatively, to select a typicallypre-made device that has a good fit with a patient's articular anatomy.The device can have a surface and shape that will match all or portionsof the articular or bone surface and shape, e.g. similar to a “mirrorimage.” The device can include apertures, slots and/or holes toaccommodate surgical instruments such as drills, reamers, curettes,k-wires, screws and saws.

Typically, a position will be chosen that will result in an anatomicallydesirable cut plane, drill hole, or general instrument orientation forsubsequent placement of an articular repair system or for facilitatingplacement of the articular repair system. Moreover, the device can bedesigned so that the depth of the drill, reamer or other surgicalinstrument can be controlled, e.g., the drill cannot go any deeper intothe tissue than defined by the device, and the size of the hole in theblock can be designed to essentially match the size of the implant.Information about other joints or axis and alignment information of ajoint or extremity can be included when selecting the position of theseslots or holes. Alternatively, the openings in the device can be madelarger than needed to accommodate these instruments. The device can alsobe configured to conform to the articular shape. The apertures, oropenings, provided can be wide enough to allow for varying the positionor angle of the surgical instrument, e.g., reamers, saws, drills,curettes and other surgical instruments. An instrument guide, typicallycomprised of a relatively hard material, can then be applied to thedevice. The device helps orient the instrument guide relative to thethree-dimensional anatomy of the joint.

The surgeon can, optionally, make fine adjustments between the alignmentdevice and the instrument guide. In this manner, an optimal compromisecan be found, for example, between biomechanical alignment and jointlaxity or biomechanical alignment and joint function, e.g. in a kneejoint flexion gap and extension gap. By oversizing the openings in thealignment guide, the surgeon can utilize the instruments and insert themin the instrument guide without damaging the alignment guide. Thus, inparticular if the alignment guide is made of plastic, debris will not beintroduced into the joint. The position and orientation between thealignment guide and the instrument guide can be also be optimized withthe use of, for example, interposed spacers, wedges, screws and othermechanical or electrical methods known in the art.

A surgeon may desire to influence joint laxity as well as jointalignment. This can be optimized for different flexion and extension,abduction, or adduction, internal and external rotation angles. For thispurpose, for example, spacers can be introduced that are attached orthat are in contact with one or more molds. The surgeon canintraoperatively evaluate the laxity or tightness of a joint usingspacers with different thickness or one or more spacers with the samethickness. For example, spacers can be applied in a knee joint in thepresence of one or more molds and the flexion gap can be evaluated withthe knee joint in flexion. The knee joint can then be extended and theextension gap can be evaluated. Ultimately, the surgeon will select anoptimal combination of spacers for a given joint and mold. A surgicalcut guide can be applied to the mold with the spacers optionallyinterposed between the mold and the cut guide. In this manner, the exactposition of the surgical cuts can be influenced and can be adjusted toachieve an optimal result. Someone skilled in the art will recognizeother means for optimizing the position of the surgical cuts. Forexample, expandable or ratchet-like devices can be utilized that can beinserted into the joint or that can be attached or that can touch themold. Hinge-like mechanisms are applicable. Similarly, jack-likemechanisms are useful. In principal, any mechanical or electrical deviceuseful for fine-tuning the position of the cut guide relative to themolds can be used.

A surgeon may desire to influence joint laxity as well as jointalignment. This can be optimized for different flexion and extension,abduction, or adduction, internal and external rotation angles. For thispurpose, for example, spacers can be introduced that are attached orthat are in contact with one or more molds. The surgeon canintraoperatively evaluate the laxity or tightness of a joint usingspacers with different thickness or one or more spacers with the samethickness. For example, spacers can be applied in a knee joint in thepresence of one or more molds and the flexion gap can be evaluated withthe knee joint in flexion. The knee joint can then be extended and theextension gap can be evaluated. Ultimately, the surgeon will select anoptimal combination of spacers for a given joint and mold. A surgicalcut guide can be applied to the mold with the spacers optionallyinterposed between the mold and the cut guide. In this manner, the exactposition of the surgical cuts can be influenced and can be adjusted toachieve an optimal result. Someone skilled in the art will recognizeother means for optimizing the position of the surgical cuts. Forexample, expandable or ratchet-like devices can be utilized that can beinserted into the joint or that can be attached or that can touch themold. Hinge-like mechanisms are applicable. Similarly, jack-likemechanisms are useful. In principal, any mechanical or electrical deviceuseful for fine-tuning the position of the cut guide relative to themolds can be used.

The molds and any related instrumentation such as spacers or ratchetscan be combined with a tensiometer to provide a better intraoperativeassessment of the joint. The tensiometer can be utilized to furtheroptimize the anatomic alignment and tightness of the joint and toimprove post-operative function and outcomes. Optionally local contactpressures may be evaluated intraoperatively, for example using a sensorlike the ones manufactured by Tekscan, South Boston, Mass.

The mold or alignment guide can be made of a plastic or polymer. Inother embodiments, the mold or portions of the mold can be made ofmetal. Metal inserts may be applied to plastic components. For example,a plastic mold may have an opening to accept a reaming device or a saw.A metal insert may be used to provide a hard wall to accept the reameror saw. Using this or similar designs can be useful to avoid theaccumulation of plastic or other debris in the joint when the saw orother surgical instruments may get in contact with the mold.

The molds may not only be used for assisting the surgical technique andguiding the placement and direction of surgical instruments. Inaddition, the molds can be utilized for guiding the placement of theimplant or implant components. For example, in the hip joint, tilting ofthe acetabular component is a frequent problem with total hiparthroplasty. A mold can be applied to the acetabular wall with anopening in the center large enough to accommodate the acetabularcomponent that the surgeon intends to place. The mold can havereceptacles or notches that match the shape of small extensions that canbe part of the implant or that can be applied to the implant. Forexample, the implant can have small members or extensions applied to thetwelve o'clock and six o'clock positions. See, for example, FIG. 29 A-D,discussed below. By aligning these members with notches or receptaclesin the mold, the surgeon can ensure that the implant is inserted withouttilting or rotation. These notches or receptacles can also be helpful tohold the implant in place while bone cement is hardening in cementeddesigns.

One or more molds can be used during the surgery. For example, in thehip, a mold can be initially applied to the proximal femur that closelyapproximates the 3D anatomy prior to the resection of the femoral head.The mold can include an opening to accommodate a saw (see FIGS. 28-29).The opening is positioned to achieve an optimally placed surgical cutfor subsequent reaming and placement of the prosthesis. A second moldcan then be applied to the proximal femur after the surgical cut hasbeen made. The second mold can be useful for guiding the direction of areamer prior to placement of the prosthesis. As can be seen in this, aswell as in other examples, molds can be made for joints prior to anysurgical intervention. However, it is also possible to make molds thatare designed to fit to a bone or portions of a joint after the surgeonhas already performed selected surgical procedures, such as cutting,reaming, drilling, etc. The mold can account for the shape of the boneor the joint resulting from these procedures.

In certain embodiments, the surgical assistance device comprises anarray of adjustable, closely spaced pins (e.g., plurality ofindividually moveable mechanical elements). One or more electronicimages or intraoperative measurements can be obtained providing objectcoordinates that define the articular and/or bone surface and shape.These objects' coordinates can be entered or transferred into thedevice, for example manually or electronically, and the information canbe used to create a surface and shape that will match all or portions ofthe articular and/or bone surface and shape by moving one or more of theelements, e.g. similar to an “image.” The device can include slots andholes to accommodate surgical instruments such as drills, curettes,k-wires, screws and saws. The position of these slots and holes can beadjusted by moving one or more of the mechanical elements. Typically, aposition will be chosen that will result in an anatomically desirablecut plane, reaming direction, or drill hole or instrument orientationfor subsequent placement of an articular repair system or forfacilitating the placement of an articular repair system. Informationabout other joints or axis and alignment information of a joint orextremity can be included when selecting the position of these slots orholes.

FIG. 22 shows an example of a surgical tool 410 having one surface 400matching the geometry of an articular surface of the joint. Also shownis an aperture 415 in the tool 410 capable of controlling drill depthand width of the hole and allowing implantation or insertion of implant420 having a press-fit design.

In another embodiment, a frame can be applied to the bone or thecartilage in areas other than the diseased bone or cartilage. The framecan include holders and guides for surgical instruments. The frame canbe attached to one or preferably more previously defined anatomicreference points. Alternatively, the position of the frame can becross-registered relative to one, or more, anatomic landmarks, using animaging test or intraoperative measurement, for example one or morefluoroscopic images acquired intraoperatively. One or more electronicimages or intraoperative measurements including using mechanical devicescan be obtained providing object coordinates that define the articularand/or bone surface and shape. These objects' coordinates can be enteredor transferred into the device, for example manually or electronically,and the information can be used to move one or more of the holders orguides for surgical instruments. Typically, a position will be chosenthat will result in a surgically or anatomically desirable cut plane ordrill hole orientation for subsequent placement of an articular repairsystem. Information about other joints or axis and alignment informationof a joint or extremity can be included when selecting the position ofthese slots or holes.

Furthermore, re-useable tools (e.g., molds) can be also be created andemployed. Non-limiting examples of re-useable materials include puttiesand other deformable materials (e.g., an array of adjustable closelyspaced pins that can be configured to match the topography of a jointsurface). In other embodiments, the molds may be made using balloons.The balloons can optionally be filled with a hardening material. Asurface can be created or can be incorporated in the balloon that allowsfor placement of a surgical cut guide, reaming guide, drill guide orplacement of other surgical tools. The balloon or other deformablematerial can be shaped intraoperatively to conform to at least onearticular surface. Other surfaces can be shaped in order to be parallelor perpendicular to anatomic or biomechanical axes. The anatomic orbiomechanical axes can be found using an intraoperative imaging test orsurgical tools commonly used for this purpose in hip, knee or otherarthroplasties.

In these embodiments, the mold can be created directly from the jointduring surgery or, alternatively, created from an image of the joint,for example, using one or more computer programs to determine objectcoordinates defining the surface contour of the joint and transferring(e.g., dialing-in) these co-ordinates to the tool. Subsequently, thetool can be aligned accurately over the joint and, accordingly, thesurgical instrument guide or the implant will be more accurately placedin or over the articular surface.

In both single-use and re-useable embodiments, the tool can be designedso that the instrument controls the depth and/or direction of the drill,i.e., the drill cannot go any deeper into the tissue than the instrumentallows, and the size of the hole or aperture in the instrument can bedesigned to essentially match the size of the implant. The tool can beused for general prosthesis implantation, including, but not limited to,the articular repair implants described herein and for reaming themarrow in the case of a total arthroplasty.

These surgical tools (devices) can also be used to remove an area ofdiseased cartilage and underlying bone or an area slightly larger thanthe diseased cartilage and underlying bone. In addition, the device canbe used on a “donor,” e.g., a cadaveric specimen, to obtain implantablerepair material. The device is typically positioned in the same generalanatomic area in which the tissue was removed in the recipient. Theshape of the device is then used to identify a donor site providing aseamless or near seamless match between the donor tissue sample and therecipient site. This can be achieved by identifying the position of thedevice in which the articular surface in the donor, e.g. a cadavericspecimen, has a seamless or near seamless contact with the inner surfacewhen applied to the cartilage.

The device can be molded, machined or formed based on the size of thearea of diseased cartilage and based on the curvature of the cartilageor the underlying subchondral bone or a combination of both. The moldingcan take into consideration surgical removal of, for example, themeniscus, in arriving at a joint surface configuration. The device canthen be applied to the donor, (e.g., a cadaveric specimen) and the donortissue can be obtained with use of a blade or saw or other tissueremoving device. The device can then be applied to the recipient in thearea of the diseased cartilage and the diseased cartilage and underlyingbone can be removed with use of a blade or saw or other tissue cuttingdevice whereby the size and shape of the removed tissue containing thediseased cartilage will closely resemble the size and shape of the donortissue. The donor tissue can then be attached to the recipient site. Forexample, said attachment can be achieved with use of screws or pins(e.g., metallic, non-metallic or bioresorable) or other fixation meansincluding but not limited to a tissue adhesive. Attachment can bethrough the cartilage surface or alternatively, through the marrowspace.

The implant site can be prepared with use of a robotic device. Therobotic device can use information from an electronic image forpreparing the recipient site.

Identification and preparation of the implant site and insertion of theimplant can be supported by asurgical navigation system. In such asystem, the position or orientation of a surgical instrument withrespect to the patient's anatomy can be tracked in real-time in one ormore 2D or 3D images. These 2D or 3D images can be calculated fromimages that were acquired preoperatively, such as MR or CT images.Non-image based surgical navigation systems that find axes or anatomicalstructures, for example with use of joint motion, can also be used. Theposition and orientation of the surgical instrument as well as the moldincluding alignment guides, surgical instrument guides, reaming guides,drill guides, saw guides, etc. can be determined from markers attachedto these devices. These markers can be located by a detector using, forexample, optical, acoustical or electromagnetic signals.

Identification and preparation of the implant site and insertion of theimplant can also be supported with use of a C-arm system. The C-armsystem can afford imaging of the joint in one or, preferably, multipleplanes. The multiplanar imaging capability can aid in defining the shapeof an articular surface. This information can be used to selected animplant with a good fit to the articular surface. Currently availableC-arm systems also afford cross-sectional imaging capability, forexample for identification and preparation of the implant site andinsertion of the implant. C-arm imaging can be combined withadministration of radiographic contrast.

In still other embodiments, the surgical devices described herein caninclude one or more materials that harden to form a mold of thearticular surface. A wide-variety of materials that harden in situ havebeen described above including polymers that can be triggered to undergoa phase change, for example polymers that are liquid or semi-liquid andharden to solids or gels upon exposure to air, application ofultraviolet light, visible light, exposure to blood, water or otherionic changes. (See, also, U.S. Pat. No. 6,443,988 to Felt et al. issuedSep. 3, 2002 and documents cited therein). Non-limiting examples ofsuitable curable and hardening materials include polyurethane materials(e.g., U.S. Pat. Nos. 6,443,988 to Felt et al., 5,288,797 to Khalilissued Feb. 22, 1994, 4,098,626 to Graham et al. issued Jul. 4, 1978 and4,594,380 to Chapin et al. issued Jun. 10, 1986; and Lu et al. (2000)BioMaterials 21(15):1595-1605 describing porous poly(L-lactide acidfoams); hydrophilic polymers as disclosed, for example, in U.S. Pat. No.5,162,430; hydrogel materials such as those described in Wake et al.(1995) Cell Transplantation 4(3):275-279, Wiese et al. (2001) J.Biomedical Materials Research 54(2):179-188 and Marler et al. (2000)Plastic Reconstruct. Surgery 105(6):2049-2058; hyaluronic acid materials(e.g., Duranti et al. (1998) Dermatologic Surgery 24(12):1317-1325);expanding beads such as chitin beads (e.g., Yusof et al. (2001) J.Biomedical Materials Research 54(1):59-68); crystal free metals such asLiquidmetals®, and/or materials used in dental applications (See, e.g.,Brauer and Antonucci, “Dental Applications” pp. 257-258 in “ConciseEncyclopedia of Polymer Science and Engineering” and U.S. Pat. No.4,368,040 to Weissman issued Jan. 11, 1983). Any biocompatible materialthat is sufficiently flowable to permit it to be delivered to the jointand there undergo complete cure in situ under physiologically acceptableconditions can be used. The material can also be biodegradable.

The curable materials can be used in conjunction with a surgical tool asdescribed herein. For example, the surgical tool can include one or moreapertures therein adapted to receive injections and the curablematerials can be injected through the apertures. Prior to solidifying insitu the materials will conform to the articular surface facing thesurgical tool and, accordingly, will form a mirror image impression ofthe surface upon hardening, thereby recreating a normal or near normalarticular surface. In addition, curable materials or surgical tools canalso be used in conjunction with any of the imaging tests and analysisdescribed herein, for example by molding these materials or surgicaltools based on an image of a joint.

FIG. 23 is a flow chart illustrating the steps involved in designing amold for use in preparing a joint surface. Typically, the first step isto measure the size of the area of the diseased cartilage or cartilageloss 2100, Once the size of the cartilage loss has been measured, theuser can measure the thickness of the adjacent cartilage 2120, prior tomeasuring the curvature of the articular surface and/or the subchondralbone 2130. Alternatively, the user can skip the step of measuring thethickness of the adjacent cartilage 2102. Once an understanding anddetermination of the nature of the cartilage defect is determined,either a mold can be selected from a library of molds 3132 or a patientspecific mold can be generated 2134. In either event, the implantationsite is then prepared 2140 and implantation is performed 2142. Any ofthese steps can be repeated by the optional repeat steps 2101, 2121,2131, 2133, 2135, 2141.

A variety of techniques can be used to derive the shape of the mold. Forexample, a few selected CT slices through the hip joint, along with afull spiral CT through the knee joint and a few selected slices throughthe ankle joint can be used to help define the axes if surgery iscontemplated of the knee joint. Once the axes are defined, the shape ofthe subchondral bone can be derived, followed by applying standardizedcartilage loss. Other more sophisticated scanning procedures can be usedto derive this information without departing from the scope of theinvention.

Turning now to tools for specific joint applications which are intendedto teach the concept of the design as it would then apply to otherjoints in the body:

i. Knee Joint

When a total knee arthroplasty is contemplated, the patient can undergoan imaging test, as discussed in more detail above, that willdemonstrate the articular anatomy of a knee joint, e.g. width of thefemoral condyles, the tibial plateau etc. Additionally, other joints canbe included in the imaging test thereby yielding information on femoraland tibial axes, deformities such as varus and valgus and otherarticular alignment. The imaging test can be an x-ray image, preferablyin standing, load-bearing position, a CT scan or an MRI scan orcombinations thereof. The articular surface and shape as well asalignment information generated with the imaging test can be used toshape the surgical assistance device, to select the surgical assistancedevice from a library of different devices with pre-made shapes andsizes, or can be entered into the surgical assistance device and can beused to define the preferred location and orientation of saw guides ordrill holes or guides for reaming devices or other surgical instruments.Intraoperatively, the surgical assistance device is applied to thetibial plateau and subsequently the femoral condyle(s) by matching itssurface with the articular surface or by attaching it to anatomicreference points on the bone or cartilage. The surgeon can thenintroduce a reamer or saw through the guides and prepare the joint forthe implantation. By cutting the cartilage and bone along anatomicallydefined planes, a more reproducible placement of the implant can beachieved. This can ultimately result in improved postoperative resultsby optimizing biomechanical stresses applied to the implant andsurrounding bone for the patient's anatomy and by minimizing axismalalignment of the implant. In addition, the surgical assistance devicecan greatly reduce the number of surgical instruments needed for totalor unicompartmental knee arthroplasty. Thus, the use of one or moresurgical assistance devices can help make joint arthroplasty moreaccurate, improve postoperative results, improve long-term implantsurvival, reduce cost by reducing the number of surgical instrumentsused. Moreover, the use of one or more surgical assistance device canhelp lower the technical difficulty of the procedure and can helpdecrease operating room (“OR”) times.

Thus, surgical tools described herein can also be designed and used tocontrol drill alignment, depth and width, for example when preparing asite to receive an implant. For example, the tools described herein,which typically conform to the joint surface, can provide for improveddrill alignment and more accurate placement of any implant. Ananatomically correct tool can be constructed by a number of methods andcan be made of any material, preferably a translucent material such asplastic, Lucite, silastic, SLA or the like, and typically is ablock-like shape prior to molding.

FIG. 24 A depicts, in cross-section, an example of a mold 600 for use onthe tibial surface having an upper surface 620. The mold 600 contains anaperture 625 through which a surgical drill or saw can fit. The apertureguides the drill or saw to make the proper hole or cut in the underlyingbone 610 as illustrated in FIGS. 21 B-D. Dotted lines 632 illustratewhere the cut corresponding to the aperture will be made in bone.

FIG. 24 B depicts, a mold 608 suitable for use on the femur. As can beappreciated from this perspective, additional apertures are provided toenable additional cuts to the bone surface. The apertures 605 enablecuts 606 to the surface of the femur. The resulting shape of the femurcorresponds to the shape of the interior surface of the femoral implant,typically as shown in FIG. 21 E. Additional shapes can be achieved, ifdesired, by changing the size, orientation and placement of theapertures. Such changes would be desired where, for example, theinterior shape of the femoral component of the implant requires adifferent shape of the prepared femur surface.

Turning now to FIG. 25, a variety of illustrations are provided showinga tibial cutting block and mold system. FIG. 25 A illustrates the tibialcutting block 2300 in conjunction with a tibia 2302 that has not beenresected. In this depiction, the cutting block 2300 consists of at leasttwo pieces. The first piece is a patient specific interior piece 2310 ormold that is designed on its inferior surface 2312 to mate, orsubstantially mate, with the existing geography of the patient's tibia2302. The superior surface 2314 and side surfaces 2316 of the firstpiece 2310 are configured to mate within the interior of an exteriorpiece 2320. The reusable exterior piece 2320 fits over the interiorpiece 2310. The system can be configured to hold the mold onto the bone.

The reusable exterior piece has a superior surface 2322 and an inferiorsurface 2324 that mates with the first piece 2310. The reusable exteriorpiece 2320 includes cutting guides 2328, to assist the surgeon inperforming the tibial surface cut described above. As shown herein aplurality of cutting guides can be provided to provide the surgeon avariety of locations to choose from in making the tibial cut. Ifnecessary, additional spacers can be provided that fit between the firstpatient configured, or molded, piece 2310 and the second reusableexterior piece, or cutting block, 2320.

The variable nature of the interior piece facilitates obtaining the mostaccurate cut despite the level of disease of the joint because itpositions the exterior piece 2320 such that it can achieve a cut that isperpendicular to the mechanical axis. Either the interior piece 2310 orthe exterior piece 2320 can be formed out of any of the materialsdiscussed above in Section II, or any other suitable material.Additionally, a person of skill in the art will appreciate that theinvention is not limited to the two piece configuration describedherein. The reusable exterior piece 2320 and the patient specificinterior piece 2310 can be a single piece that is either patientspecific (where manufacturing costs of materials support such a product)or is reusable based on a library of substantially defect conformingshapes developed in response to known or common tibial surface sizes anddefects.

The interior piece 2310 is typically molded to the tibia including thesubchondral bone and/or the cartilage. The surgeon will typically removeany residual meniscal tissue prior to applying the mold. Optionally, theinterior surface 2312 of the mold can include shape information ofportions or all of the menisci.

Turning now to FIG. 25 B-D, a variety of views of the removable exteriorpiece 2320. The top surface 2322 of the exterior piece can be relativelyflat. The lower surface 2324 which abuts the interior piece conforms tothe shape of the upper surface of the interior piece. In thisillustration the upper surface of the interior piece is flat, thereforethe lower surface 2324 of the reusable exterior surface is also flat toprovide an optimal mating surface.

A guide plate 2326 is provided that extends along the side of at least aportion of the exterior piece 2320. The guide plate 2326 provides one ormore slots or guides 2328 through which a saw blade can be inserted toachieve the cut desired of the tibial surface. Additionally, the slot,or guide, can be configured so that the saw blade cuts at a lineperpendicular to the mechanical axis, or so that it cuts at a line thatis perpendicular to the mechanical axis, but has a 4-7° slope in thesagittal plane to match the normal slope of the tibia.

Optionally, a central bore 2330 can be provided that, for example,enables a drill to ream a hole into the bone for the stem of the tibialcomponent of the knee implant.

FIGS. 25 E-H illustrate the interior, patient specific, piece 2310 froma variety of perspectives. FIG. 25 E shows a side view of the pieceshowing the uniform superior surface 2314 and the uniform side surfaces2316 along with the irregular inferior surface 2316. The inferiorsurface mates with the irregular surface of the tibia 2302. FIG. 25 Fillustrates a superior view of the interior, patient, specific piece ofthe mold 2310. Optionally having an aperture 2330. FIG. 25 G illustratesan inferior view of the interior patient specific mold piece 2310further illustrating the irregular surface which includes convex andconcave portions to the surface, as necessary to achieve optimal matingwith the surface of the tibia. FIG. 25 H illustrates cross-sectionalviews of the interior patient specific mold piece 2310. As can be seenin the cross-sections, the surface of the interior surface changes alongits length.

As is evident from the views shown in FIGS. 25 B and D, the length ofthe guide plate 2326 can be such that it extends along all or part ofthe tibial plateau, e.g. where the guide plate 2326 is asymmetricallypositioned as shown in FIG. 25 B or symmetrical as in FIG. 23 D. Iftotal knee arthroplasty is contemplated, the length of the guide plate2326 typically extends along all of the tibial plateau. Ifunicompartmental arthroplasty is contemplated, the length of the guideplate typically extends along the length of the compartment that thesurgeon will operate on. Similarly, if total knee arthroplasty iscontemplated, the length of the molded, interior piece 2310 typicallyextends along all of the tibial plateau; it can include one or bothtibial spines. If unicompartmental arthroplasty is contemplated, thelength of the molded interior piece typically extends along the lengthof the compartment that the surgeon will operate on; it can optionallyinclude a tibial spine.

Turning now to FIG. 25 I, an alternative embodiment is depicted of theaperture 2330. In this embodiment, the aperture features lateralprotrusions to accommodate using a reamer or punch to create an openingin the bone that accepts a stem having flanges.

FIGS. 25 J and M depict alternative embodiments of the inventiondesigned to control the movement and rotation of the cutting block 2320relative to the mold 2310. As shown in FIG. 25 J a series ofprotrusions, illustrated as pegs 2340, are provided that extend from thesuperior surface of the mold. As will be appreciated by those of skillin the art, one or more pegs or protrusions can be used withoutdeparting from the scope of the invention. For purposes of illustration,two pegs have been shown in FIG. 25 J. Depending on the control desired,the pegs 2340 are configured to fit within, for example, a curved slot2342 that enables rotational adjustment as illustrated in FIG. 23 K orwithin a recess 2344 that conforms in shape to the peg 2340 as shown inFIG. 25 L. As will be appreciated by those of skill in the art, therecess 2344 can be sized to snugly encompass the peg or can be sizedlarger than the peg to allow limited lateral and rotational movement.

As illustrated in FIG. 25 M the surface of the mold 2310 can beconfigured such that the upper surface forms a convex dome 2350 thatfits within a concave well 2352 provided on the interior surface of thecutting block 2320. This configuration enables greater rotationalmovement about the mechanical axis while limiting lateral movement ortranslation.

Other embodiments and configurations could be used to achieve theseresults without departing from the scope of the invention.

As will be appreciated by those of skill in the art, more than twopieces can be used, where appropriate, to comprise the system. Forexample, the patient specific interior piece 2310 can be two pieces thatare configured to form a single piece when placed on the tibia.Additionally, the exterior piece 2320 can be two components. The firstcomponent can have, for example, the cutting guide apertures 2328. Afterthe resection using the cutting guide aperture 2328 is made, theexterior piece 2320 can be removed and a secondary exterior piece 2320′can be used which does not have the guide plate 2326 with the cuttingguide apertures 2328, but has the aperture 2330 which facilitates boringinto the tibial surface an aperture to receive a stem of the tibialcomponent of the knee implant. Any of these designs could also featurethe surface configurations shown in FIGS. 25 J-M, if desired.

FIG. 25 N illustrates an alternative design of the cutting block 2320that provides additional structures 2360 to protect, for example, thecruciate ligaments, from being cut during the preparation of the tibialplateau. These additional structures can be in the form of indentedguides 2360, as shown in FIG. 25 N or other suitable structures.

FIG. 25 O illustrates a cross-section of a system having anchoring pegs2362 on the surface of the interior piece 2310 that anchor the interiorpiece 2310 into the cartilage or meniscal area.

FIGS. 25 P AND Q illustrate a device 2300 configured to cover half of atibial plateau such that it is unicompartmental.

Turning now to FIG. 26, a femoral mold system is depicted thatfacilitates preparing the surface of the femur such that the finallyimplanted femoral implant will achieve optimal mechanical and anatomicalaxis alignment.

FIG. 26 A illustrates the femur 2400 with a first portion 2410 of themold placed thereon. In this depiction, the top surface of the mold 2412is provided with a plurality of apertures. In this instance theapertures consist of a pair of rectangular apertures 2414, a pair ofsquare apertures 2416, a central bore aperture 2418 and a longrectangular aperture 2420. The side surface 2422 of the first portion2410 also has a rectangular aperture 2424. Each of the apertures islarger than the eventual cuts to be made on the femur so that, in theevent the material the first portion of the mold is manufactured from asoft material, such as plastic, it will not be inadvertently cut duringthe joint surface preparation process. Additionally, the shapes can beadjusted, e.g., rectangular shapes made trapezoidal, to give a greaterflexibility to the cut length along one area, without increasingflexibility in another area. As will be appreciated by those of skill inthe art, other shapes for the apertures, or orifices, can be changedwithout departing from the scope of the invention.

FIG. 26 B illustrates a side view of the first portion 2410 from theperspective of the side surface 2422 illustrating the aperture 2424. Asillustrated, the exterior surface 2411 has a uniform surface which isflat, or relatively flat configuration while the interior surface 2413has an irregular surface that conforms, or substantially conforms, withthe surface of the femur.

FIG. 26 C illustrates another side view of the first, patient specificmolded, portion 2410, more particularly illustrating the irregularsurface 2413 of the interior. FIG. 26 D illustrates the first portion2410 from a top view. The center bore aperture 2418 is optionallyprovided to facilitate positioning the first piece and to preventcentral rotation.

FIG. 26 D illustrates a top view of the first portion 2410. The bottomof the illustration corresponds to an anterior location relative to theknee joint. From the top view, each of the apertures is illustrated asdescribed above. As will be appreciated by those of skill in the art,the apertures can be shaped differently without departing from the scopeof the invention.

Turning now to FIG. 26 E, the femur 2400 with a first portion 2410 ofthe cutting block placed on the femur and a second, exterior, portion2440 placed over the first portion 2410 is illustrated. The second,exterior, portion 2440 features a series of rectangular grooves(2442-2450) that facilitate inserting a saw blade therethrough to makethe cuts necessary to achieve the femur shape illustrated in FIG. 21 E.These grooves can enable the blade to access at a 90° angle to thesurface of the exterior portion, or, for example, at a 45° angle. Otherangles are also possible without departing from the scope of theinvention.

As shown by the dashed lines, the grooves (2442-2450) of the secondportion 2440, overlay the apertures of the first layer.

FIG. 26 F illustrates a side view of the second, exterior, cutting blockportion 2440. From the side view a single aperture 2450 is provided toaccess the femur cut. FIG. 26 G is another side view of the second,exterior, portion 2440 showing the location and relative angles of therectangular grooves. As evidenced from this view, the orientation of thegrooves 2442, 2448 and 2450 is perpendicular to at least one surface ofthe second, exterior, portion 2440. The orientation of the grooves 2444,2446 is at an angle that is not perpendicular to at least one surface ofthe second, exterior portion 2440. These grooves (2444, 2446) facilitatemaking the angled chamfer cuts to the femur. FIG. 26 H is a top view ofthe second, exterior portion 2440. As will be appreciated by those ofskill in the art, the location and orientation of the grooves willchange depending upon the design of the femoral implant and the shaperequired of the femur to communicate with the implant.

FIG. 26 I illustrates a spacer 2401 for use between the first portion2410 and the second portion 2440. The spacer 2401 raises the secondportion relative to the first portion, thus raising the area at whichthe cut through groove 2424 is made relative to the surface of thefemur. As will be appreciated by those of skill in the art, more thanone spacer can be employed without departing from the scope of theinvention. Spacers can also be used for making the tibial cuts. Optionalgrooves or channels 2403 can be provided to accommodate, for example,pins 2460 shown in FIG. 26 J.

Similar to the designs discussed above with respect to FIG. 25,alternative designs can be used to control the movement and rotation ofthe cutting block 2440 relative to the mold 2410. As shown in FIG. 26 Ja series of protrusions, illustrated as pegs 2460, are provided thatextend from the superior surface of the mold. These pegs or protrusionscan be telescoping to facilitate the use of molds if necessary. As willbe appreciated by those of skill in the art, one or more pegs orprotrusions can be used without departing from the scope of theinvention. For purposes of illustration, two pegs have been shown inFIG. 26 J. Depending on the control desired, the pegs 2460 areconfigured to fit within, for example, a curved slot that enablesrotational adjustment similar to the slots illustrated in FIG. 25 K orwithin a recess that conforms in shape to the peg, similar to that shownin FIG. 25 L and described with respect to the tibial cutting system. Aswill be appreciated by those of skill in the art, the recess 2462 can besized to snugly encompass the peg or can be sized larger than the peg toallow limited lateral and rotational movement.

As illustrated in FIG. 26 K the surface of the mold 2410 can beconfigured such that the upper surface forms a convex dome 2464 thatfits within a concave well 2466 provided on the interior surface of thecutting block 2440. This configuration enables greater rotationalmovement about the mechanical axis while limiting lateral movement ortranslation.

In installing an implant, first the tibial surface is cut using a tibialblock, such as those shown in FIG. 26. The patient specific mold isplaced on the femur. The knee is then placed in extension and spacers2470, such as those shown in FIG. 26 I, or shims are used, if required,until the joint optimal function is achieved in both extension andflexion. The spacers, or shims, are typically of an incremental size,e.g., 5 mm thick to provide increasing distance as the leg is placed inextension and flexion. A tensiometer can be used to assist in thisdetermination or can be incorporated into the mold or spacers in orderto provide optimal results. The design of tensiometers are known in theart and are not included herein to avoid obscuring the invention.Suitable designs include, for example, those described in U.S. Pat. No.5,630,820 to Todd issued May 20, 1997.

As illustrated in FIGS. 26 N (sagittal view) and 26M (coronal view), theinterior surface 2413 of the mold 2410 can include small teeth 2465 orextensions that can help stabilize the mold against the cartilage 2466or subchondral bone 2467.

Turning now to FIG. 27, a variety of illustrations are provided showinga patellar cutting block and mold system. FIGS. 27 A-C illustrates thepatellar cutting block 2700 in conjunction with a patella 2702 that hasnot been resected. In this depiction, the cutting block 2700 can consistof only one piece or a plurality of pieces, if desired. The innersurface 2703 is patient specific and designed to mate, or substantiallymate, with the existing geography of the patient's patella 2702. Smallopenings are present 2707 to accept the saw. The mold or block can haveonly one or multiple openings. The openings can be larger than the sawin order to allow for some rotation or other fine adjustments. FIG. 27 Ais a view in the sagittal plane S. The quadriceps tendon 2704 andpatellar tendon 2705 are shown.

FIG. 27 B is a view in the axial plane A. The cartilage 2706 is shown.The mold can be molded to the cartilage or the subchondral bone orcombinations thereof. FIG. 27 C is a frontal view F of the molddemonstrating the opening for the saw 2707. The dashed line indicatesthe relative position of the patella 2702.

FIGS. 27 D (sagittal view) and E (axial view) illustrate a patellarcutting block 2708 in conjunction with a patella 2702 that has not beenresected. In this depiction, the cutting block 2708 consists of at leasttwo pieces. The first piece is a patient specific interior piece 2710 ormold that is designed on its inferior surface 2712 to mate, orsubstantially mate, with the existing geography of the patient's patella2702. The posterior surface 2714 and side surfaces 2716 of the firstpiece 2710 are configured to mate within the interior of an exteriorpiece 2720. The reusable exterior piece 2720 fits over the interiorpiece 2710 and holds it onto the patella. The reusable exterior piecehas an interior surface 2724 that mates with the first piece 2710. Thereusable exterior piece 2720 includes cutting guides 2707, to assist thesurgeon in performing the patellar surface cut. A plurality of cuttingguides can be provided to provide the surgeon a variety of locations tochoose from in making the patellar cut. If necessary, additional spacerscan be provided that fit between the first patient configured, ormolded, piece 2710 and the second reusable exterior piece, or cuttingblock, 2720.

The second reusable exterior piece, or cutting block, 2720, can havegrooves 2722 and extensions 2725 designed to mate with surgicalinstruments such as a patellar clamp 2726. The patellar clamp 2726 canhave ring shaped graspers 2728 and locking mechanisms, for exampleratchet-like 2730. The opening 2732 in the grasper fits onto theextension 2725 of the second reusable exterior piece 2720. Portions of afirst portion of the handle of the grasper can be at an oblique angle2734 relative to the second portion of the handle, or curved (notshown), in order to facilitate insertion. Typically the portion of thegrasper that will be facing towards the intra-articular side will havean oblique or curved shaped thereby allowing a slightly smallerincision.

The variable nature of the interior piece facilitates obtaining the mostaccurate cut despite the level of disease of the joint because itpositions the exterior piece 2720 in the desired plane. Either theinterior piece 2710 or the exterior piece 2720 can be formed out of anyof the materials discussed above in Section II, or any other suitablematerial. Additionally, a person of skill in the art will appreciatethat the invention is not limited to the two piece configurationdescribed herein. The reusable exterior piece 2720 and the patientspecific interior piece 2710 can be a single piece that is eitherpatient specific (where manufacturing costs of materials support such aproduct) or is reusable based on a library of substantially defectconforming shapes developed in response to known or common tibialsurface sizes and defects.

The interior piece 2710 is typically molded to the patella including thesubchondral bone and/or the cartilage.

From this determination, an understanding of the amount of space neededto balance the knee is determined and an appropriate number of spacersis then used in conjunction with the cutting block and mold to achievethe cutting surfaces and to prevent removal of too much bone. Where thecutting block has a thickness of, for example, 10 mm, and each spacerhas a thickness of 5 mm, in preparing the knee for cuts, two of thespacers would be removed when applying the cutting block to achieve thecutting planes identified as optimal during flexion and extension.Similar results can be achieved with ratchet or jack like designsinterposed between the mold and the cut guide.

ii. Hip Joint

Turning now to FIG. 28, a variety of views showing sample mold andcutting block systems for use in the hip joint are shown. FIG. 28 Aillustrates femur 2510 with a mold and cutting block system 2520 placedto provide a cutting plane 2530 across the femoral neck 2512 tofacilitate removal of the head 2514 of the femur and creation of asurface 2516 for the hip ball prosthesis.

FIG. 28 B illustrates a top view of the cutting block system 2520. Thecutting block system 2520 includes an interior, patient specific, moldedsection 2524 and an exterior cutting block surface 2522. The interior,patient specific, molded section 2524 can include a canal 2526 tofacilitate placing the interior section 2524 over the neck of the femur.As will be appreciated by those of skill in the art, the width of thecanal will vary depending upon the rigidity of the material used to makethe interior molded section. The exterior cutting block surface 2522 isconfigured to fit snugly around the interior section. Additionalstructures can be provided, similar to those described above withrespect to the knee cutting block system, that control movement of theexterior cutting block 2524 relative to interior mold section 2522, aswill be appreciated by those of skill in the art. Where the interiorsection 2524 encompasses all or part of the femoral neck, the cuttingblock system can be configured such that it aids in removal of thefemoral head once the cut has been made by, for example, providing ahandle 2501.

FIG. 28 C illustrates a second cutting block system 2550 that can beplaced over the cut femur to provide a guide for reaming after thefemoral head has been removed using the cutting block shown in FIG. 28A. FIG. 28 D is a top view of the cutting block shown in FIG. 28 c. Aswill be appreciated by those of skill in the art, the cutting blockshown in FIG. 28 c-D, can be one or more pieces. As shown in FIG. 28 E,the aperture 2552 can be configured such that it enables the reaming forthe post of the implant to be at a 90° angle relative to the surface offemur. Alternatively, as shown in FIG. 28 F, the aperture 2552 can beconfigured to provide an angle other than 90° for reaming, if desired.

FIGS. 29 A (sagittal view) and 29 B (frontal view, down onto mold)illustrates a mold system 2955 for the acetabulum 2957. The mold canhave grooves 2959 that stabilize it against the acetabular rim 2960.Surgical instruments, e.g. reamers, can be passed through an opening inthe mold 2956. The side wall of the opening 2962 can guide the directionof the reamer or other surgical instruments. Metal sleeves 2964 can beinserted into the side wall 2962 thereby protecting the side wall of themold from damage. The metal sleeves 2964 can have lips 2966 oroverhanging edges that secure the sleeve against the mold and help avoidmovement of the sleeve against the articular surface.

FIG. 29 C is a frontal view of the same mold system shown in FIGS. 29 Aand 29 B. A groove 2970 has been added at the 6 and 12 o'clockpositions. The groove can be used for accurate positioning or placementof surgical instruments. Moreover, the groove can be useful for accurateplacement of the acetabular component without rotational error. Someoneskilled in the art will recognize that more than one groove or internalguide can be used in order to not only reduce rotational error but alsoerror related to tilting of the implant. As seen FIG. 29 D, the implant2975 can have little extensions 2977 matching the grooves therebyguiding the implant placement. The extensions 2977 can be a permanentpart of the implant design or they can be detachable. Note metal rim2979 and inner polyethylene cup 2980 of the acetabular component.

FIG. 29 D illustrates a cross-section of a system where the interiorsurface 2960 of the molded section 2924 has teeth 2962 or grooves tofacilitate grasping the neck of the femur.

iii. Small, Focal Cartilage Defect

After identification of the cartilage defect and marking of the skinsurface using the proprietary U-shaped cartilage defect locator deviceas described herein, a 3 cm incision is placed and the tissue retractorsare inserted. The cartilage defect is visualized.

A first Lucite block matching the 3D surface of the femoral condyle isplaced over the cartilage defect. The central portion of the Luciteblock contains a drill hole with an inner diameter of, for example, 1.5cm, corresponding to the diameter of the base plate of the implant. Astandard surgical drill with a drill guide for depth control is insertedthrough the Lucite block, and the recipient site is prepared for thebase component of the implant. The drill and the Lucite block are thenremoved.

A second Lucite block of identical outer dimensions is then placed overthe implant recipient site. The second Lucite block has a rounded,cylindrical extension matching the size of the first drill hole (andmatching the shape of the base component of the implant), with adiameter 0.1 mm smaller than the first drill hole and 0.2 mm smallerthan that of the base of the implant. The cylindrical extension isplaced inside the first drill hole.

The second Lucite block contains a drill hole extending from theexternal surface of the block to the cylindrical extension. The innerdiameter of the second drill hole matches the diameter of the distalportion of the fin-shaped stabilizer strut of the implant, e.g. 3 mm. Adrill, e.g. with 3 mm diameter, with a drill guide for depth control isinserted into the second hole and the recipient site is prepared for thestabilizer strut with a four fin and step design. The drill and theLucite block are then removed.

A plastic model/trial implant matching the 3-D shape of the finalimplant with a diameter of the base component of 0.2 mm less than thatof the final implant and a cylindrical rather than tapered strutstabilizer with a diameter of 0.1 mm less than the distal portion of thefinal implant is then placed inside the cartilage defect. The plasticmodel/trial implant is used to confirm alignment of the implant surfacewith the surrounding cartilage. The surgeon then performs finaladjustments.

The implant is subsequently placed inside the recipient site. Theanterior fin of the implant is marked with red color and labeled “A.”The posterior fin is marked green with a label “P” and the medial fin iscolor coded yellow with a label “M.” The Lucite block is then placedover the implant. A plastic hammer is utilized to advance the implantslowly into the recipient site. A press fit is achieved with help of thetapered and four fin design of the strut, as well as the slightlygreater diameter (0.1 mm) of the base component relative to the drillhole. The Lucite block is removed. The tissue retractors are thenremoved. Standard surgical technique is used to close the 3 cm incision.The same procedure described above for the medial femoral condyle canalso be applied to the lateral femoral condyle, the medial tibialplateau, the lateral tibial plateau and the patella. Immediatestabilization of the device can be achieved by combining it with bonecement if desired.

IV. Kits

Also described herein are kits comprising one or more of the methods,systems and/or compositions described herein. In particular, a kit caninclude one or more of the following: instructions (methods) ofobtaining electronic images; systems or instructions for evaluatingelectronic images; one or more computer means capable of analyzing orprocessing the electronic images; and/or one or more surgical tools forimplanting an articular repair system. The kits can include othermaterials, for example, instructions, reagents, containers and/orimaging aids (e.g., films, holders, digitizers, etc.).

The following examples are included to more fully illustrate the presentinvention. Additionally, these examples provide preferred embodiments ofthe invention and are not meant to limit the scope thereof.

Example 1 Design and Construction of a Three-Dimensional ArticularRepair System

Areas of cartilage are imaged as described herein to detect areas ofcartilage loss and/or diseased cartilage. The margins and shape of thecartilage and subchondral bone adjacent to the diseased areas aredetermined. The thickness of the cartilage is determined. The size ofthe articular repair system is determined based on the abovemeasurements. (FIGS. 12-14). In particular, the repair system is eitherselected (based on best fit) from a catalogue of existing, pre-madeimplants with a range of different sizes and curvatures orcustom-designed using CAD/CAM technology. The library of existing shapesis typically on the order of about 30 sizes.

The implant is a chromium cobalt implant (see also FIGS. 12-14 and17-19). The articular surface is polished and the external dimensionsslightly greater than the area of diseased cartilage. The shape isadapted to achieve perfect or near perfect joint congruity utilizingshape information of surrounding cartilage and underlying subchondralbone. Other design features of the implant can include: a slanted (60-to 70-degree angle) interface to adjacent cartilage; a broad-based basecomponent for depth control; a press fit design of base component; aporous coating of base component for ingrowth of bone and rigidstabilization; a dual peg design for large defects implantstabilization, also porous coated (FIG. 12 A); a single stabilizer strutwith tapered, four fin and step design for small, focal defects, alsoporous coated (FIG. 12 B); and a design applicable to femoralresurfacing (convex external surface) and tibial resurfacing (concaveexternal surface).

Example 2 Minimally Invasive, Arthroscopically Assisted SurgicalTechnique

The articular repair systems are inserted using arthroscopic assistance.The device does not require the 15 to 30 cm incision utilized inunicompartmental and total knee arthroplasties. The procedure isperformed under regional anesthesia, typically epidural anesthesia. Thesurgeon can apply a tourniquet on the upper thigh of the patient torestrict the blood flow to the knee during the procedure. The leg isprepped and draped in sterile technique. A stylette is used to createtwo small 2 mm ports at the anteromedial and the anterolateral aspect ofthe joint using classical arthroscopic technique. The arthroscope isinserted via the lateral port. The arthroscopic instruments are insertedvia the medial port. The cartilage defect is visualized using thearthroscope. A cartilage defect locator device is placed inside thediseased cartilage. The probe has a U-shape, with the first arm touchingthe center of the area of diseased cartilage inside the joint and thesecond arm of the U remaining outside the joint. The second arm of the Uindicates the position of the cartilage relative to the skin. Thesurgeon marks the position of the cartilage defect on the skin. A 3 cmincision is created over the defect. Tissue retractors are inserted andthe defect is visualized.

A translucent Lucite block matching the 3D shape of the adjacentcartilage and the cartilage defect is placed over the cartilage defect(FIG. 13). For larger defects, the Lucite block includes a lateral slotfor insertion of a saw. The saw is inserted and a straight cut is madeacross the articular surface, removing an area slightly larger than thediseased cartilage. The center of the Lucite block contains two drillholes with a 7.2 mm diameter. A 7.1 mm drill with drill guidecontrolling the depth of tissue penetration is inserted via the drillhole. Holes for the cylindrical pegs of the implant are created. Thedrill and the Lucite block are subsequently removed.

A plastic model/trial implant of the mini-repair system matching theouter dimensions of the implant is then inserted. The trial implant isutilized to confirm anatomic placement of the actual implant. Ifindicated, the surgeon can make smaller adjustments at this point toimprove the match, e.g. slight expansion of the drill holes oradjustment of the cut plane.

The implant is then inserted with the pegs pointing into the drillholes. Anterior and posterior positions of the implant are color-coded;specifically the anterior peg is marked with a red color and a smallletter “A”, while the posterior peg has a green color and a small letter“P”. Similarly, the medial aspect of the implant is color-coded yellowand marked with a small letter “M” and the lateral aspect of the implantis marked with a small letter “L”. The Lucite block is then placed onthe external surface of the implant and a plastic hammer is used togently advance the pegs into the drill holes. The pegs are designed toachieve a press fit.

The same technique can be applied in the tibia. The implant has aconcave articular surface matching the 3D shape of the tibial plateau.Immediate stabilization of the device can be achieved by combining itwith bone cement if desired.

The foregoing description of embodiments of the present invention hasbeen provided for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseforms disclosed. Many modifications and variations will be apparent tothe practitioner skilled in the art. The embodiments were chosen anddescribed in order to best explain the principles of the invention andits practical application, thereby enabling others skilled in the art tounderstand the invention and the various embodiments and with variousmodifications that are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the followingclaims equivalents thereof.

1. A method of generating a patient-matched surgical tool, the methodcomprising: obtaining first magnetic resonance image data associatedwith at least a portion of a joint of a patient; obtaining secondmagnetic resonance image data associated with at least a portion of asecond joint; deriving an electronic model of at least a portion of thejoint using at least the first magnetic resonance image data; creating asurgical tool using, at least in part, the electronic model; wherein thetool includes a contact surface substantially matched to a correspondingsurface of the joint and a guide for directing movement of a surgicalinstrument; and wherein the position or orientation of the guiderelative to contact surface is adapted at least in part based oninformation derived from the magnetic resonance image data associatedwith at least a portion of a second joint.
 2. A method of generating apatient-matched surgical tool, the method comprising: obtaining firstimage data associated with at least a portion of a joint of a patient;obtaining magnetic resonance image data associated with at least aportion of a second joint; deriving an electronic model of at least aportion of the joint using at least the first image data; creating asurgical tool using, at least in part, the electronic model; wherein thetool includes a contact surface substantially matched to a correspondingsurface of the joint and a guide for directing movement of a surgicalinstrument; and wherein the position or orientation of the guiderelative to contact surface is adapted at least in part based oninformation derived from the magnetic resonance image data associatedwith at least a portion of a second joint.
 3. The method of claim 2,wherein the joint is one of a hip joint, knee joint, and ankle joint. 4.The method of claim 2, further comprising identifying an anatomicallandmark using the magnetic resonance image data of the second joint. 5.The method of claim 4, further comprising utilizing the landmark atleast in part to determine an anatomic or biomechanical axis associatedwith the joint.
 6. The method of claim 4, wherein the landmark is one ofa centroid of a tibial shaft of the patient; an intercondylar notch ofthe patient, an ankle joint of the patient, a centroid of a femoral headof the patient.
 7. The method of claim 2, wherein the first image datais image data of the joint in a weight-bearing condition.
 8. The methodof claim 2, wherein the magnetic resonance image data is a full lengthimage of a leg associated with the joint.
 9. The method of claim 2,wherein the magnetic resonance image data is image data of the joint ina lying position.
 10. The method of claim 2, further comprisingestimating biomechanical axis at least in part from the magneticresonance image data.
 11. The method of claim 2, wherein the magneticresonance image data is image data obtained with the joint in anon-weight-bearing position.
 12. The method of claim 11, wherein thenon-weight-bearing image data includes the hip and ankle joint.
 13. Themethod of claim 2, further comprising determining a position of animplant.
 14. The method of claim 2, wherein the guide is aligned basedat least in part on the determined position of the implant.
 15. Themethod of claim 2, further comprising determining a position of animplant based at least in part on an epicondylar axis of the joint andwherein the guide is aligned based at least in part on the determinedposition of the implant.
 16. The method of claim 2, further comprisingdetermining a position of an implant based at least in part on ananteroposterior axis of the joint and wherein the guide is aligned basedat least in part on the determined position of the implant.
 17. Themethod of claim 2, further comprising determining a position of animplant based at least in part on a posterior condylar axis and whereinthe guide is aligned based at least in part on the determined rotationalposition of the implant.
 18. The method of claim 2, further comprisingdetermining a rotational position of an implant and wherein the guide isaligned based at least in part on the determined rotational position ofthe implant.
 19. The method of claim 2, further comprising determining asize of an implant.
 20. The method of claim 19, wherein the guide isaligned based at least in part on the determined size of the implant.21. The method of claim 2, further comprising determining a dimension ofan implant.
 22. The method of claim 21, wherein the guide is alignedbased at least in part on the determined dimension of the implant. 23.The method of claim 2, further comprising determining a mechanical axisof the joint from the magnetic resonance image data.
 24. The method ofclaim 2, further comprising determining an anatomical axis of the jointfrom the magnetic resonance image data.
 25. The method of claim 2,wherein the magnetic resonance image data is two dimensional data. 26.The method of claim 2, wherein the magnetic resonance image data isthree dimensional data.
 27. The method of claim 2, further comprisingincorporating information regarding a surgical plan and wherein thesurgical tool is created based at least in part on the information. 28.A patient specific surgical instrument for use in implanting anorthopedic implant in a patient, the process comprising: determining atleast in part from a first set of image data the surface contours of atleast a portion of a surface of or near a joint of the patient;determining at least in part from a set of magnetic resonance image dataa mechanical axis associated with the joint; incorporating apatient-specific surface into the surgical instrument such that thepatient-specific surface substantially matches the determined surfacecontours; incorporating a guide into the surgical instrument, whereinthe guide is oriented relative to the patient-specific surface based atleast in part on the determined mechanical axis.
 29. A method ofcreating a patient-specific instrument for implanting an orthopedicimplant in or about a joint of a patient, the method comprising:creating a patient-specific surgical instrument based at least in parton a first image data set and a magnetic resonance image data set,wherein the first image data set is of a type that is different from themagnetic resonance image data set; wherein the surgical instrument has apatient-specific surface that is derived from at least the first imagedata and that substantially matches a corresponding surface portionassociated with the joint; and wherein the surgical instrument has aguide that is oriented relative to the patient-specific surface based oninformation derived from the magnetic resonance image data set.
 30. Themethod of claim 29, wherein the first image data is x-ray image data.